# DERATE — Truck Fault Codes

> DERATE is a native mobile app for iOS and Android (it does not run as a web app). A truck driver photographs the dashboard or the scanner screen — no scanner needed — and DERATE reads the J1939 SPN/FMI or OBD-II code and says what it is, how urgent it is (stop now / caution / info), the estimated repair cost, and produces a report to send to the mechanic. Spanish and English.

> DERATE es una app móvil nativa para iOS y Android. El chofer toma foto del tablero o del escáner y DERATE dice qué es el código, qué tan urgente es y cuánto cuesta, con reporte para el mecánico. Español e inglés.

Full text of every guide and news article: https://derate.app/llms-full.txt

Publisher: VARGER GROUP LLC
Website: https://derate.app/ (download page only)
Who it's for: truck drivers, operators and owner-operators of heavy-duty trucks (Freightliner, Kenworth, Peterbilt, International, Volvo, Mack; Cummins, Detroit, PACCAR engines).
Supported code formats: J1939 SPN/FMI, OBD-II (Pxxxx), OEM dash telltales.
Severity semantics: RED octagon = stop now, YELLOW triangle = caution / possible derate, WHITE-GREEN circle = information only.

## Download

- App Store (iOS): https://apps.apple.com/app/id6804848638
- Google Play (Android): package com.vargergroup.derate

## Pricing

Free download. One-time $19.99 Rescue diagnosis, or monthly plans with a 7-day free trial for new subscribers. All purchases are made inside the app through the App Store or Google Play.

## Public fault code libraries

- [Biblioteca de códigos (ES)](https://derate.app/codigos)
- [Fault code library (EN)](https://derate.app/codes)
Data: DERATE verified base, updated October 2026.
- [Fault code dataset (EN)](https://derate.app/data) · [Datos de códigos (ES)](https://derate.app/datos) — CSV https://derate.app/data/derate-codes.csv and JSON https://derate.app/data/derate-codes.json, CC BY 4.0 (attribution: DERATE / VARGER Group LLC). Severity is DERATE triage; derates is yes/no only; prices are estimated part-only USD ranges.
- [Privacidad / Privacy](https://derate.app/privacy) · [Términos / Terms](https://derate.app/terms)

## Guides

Hubs: https://derate.app/guides (EN) · https://derate.app/guias (ES)

- [Check Engine Light on a Semi: Can You Keep Driving?](https://derate.app/guides/check-engine-light-semi-truck-keep-driving) · ES: [Check engine en el tráiler: ¿puedes seguir manejando?](https://derate.app/guias/check-engine-light-semi-truck-keep-driving): Amber, red or flashing? When a semi truck check engine light means keep driving, slow down or stop now, plus derate timers and what to note for the shop.
- [Cummins Fault Codes: Common ISX and X15 Codes Explained](https://derate.app/guides/cummins-fault-codes-guide) · ES: [Códigos de falla Cummins: los más comunes en ISX y X15](https://derate.app/guias/cummins-fault-codes-guide): Cummins fault codes on ISX15 and X15: how codes map to SPN/FMI, amber vs red lamps, common DEF, DPF, NOx, EGR, turbo and coolant codes, and when to stop.
- [How to Decode a Semi Truck VIN and Check Its History](https://derate.app/guides/decode-semi-truck-vin) · ES: [Cómo leer el VIN de un tráiler y revisar su historial](https://derate.app/guias/decode-semi-truck-vin): Decode a semi truck VIN: 17-character structure, truck maker WMIs, where the plate is, engine dataplate, free NHTSA decoder and recall lookup, ECM history.
- [Detroit DD15 and DD13 Fault Codes: Common Problems](https://derate.app/guides/detroit-dd15-dd13-fault-codes) · ES: [Códigos Detroit DD15 y DD13: problemas comunes](https://derate.app/guias/detroit-dd15-dd13-fault-codes): Detroit DD15 and DD13 fault codes: what the MCM, ACM and CPC control, common DPF, DEF, NOx, boost, coolant and fuel codes, and when to stop.
- [ECM Problems on a Diesel Truck: Symptoms, Codes, Cost](https://derate.app/guides/ecm-problems-diesel-truck) · ES: [Fallas del ECM en un diésel: síntomas, códigos y costo](https://derate.app/guias/ecm-problems-diesel-truck): ECM problems on a diesel truck: no start, random derates, SPN 639 datalink loss. Why a bad ECM is usually wiring, how to test, and reman vs new ECM cost.
- [ELD Malfunction Codes: What They Mean and the 8-Day Rule](https://derate.app/guides/eld-malfunction-codes) · ES: [Códigos de falla del ELD: significado y regla de 8 días](https://derate.app/guias/eld-malfunction-codes): ELD malfunction codes P, E, T, L, R, S, O and data diagnostics 1-6 explained, what the driver must do, the carrier 8-day repair rule and common causes.
- [Finding a Diesel Mechanic on the Road: A Driver's Guide](https://derate.app/guides/find-diesel-mechanic-on-the-road) · ES: [Mecánico diésel en carretera: cómo elegir bien](https://derate.app/guias/find-diesel-mechanic-on-the-road): Where to find a diesel mechanic on the road, what to ask before you authorize, red flags, typical US diagnostic fees and labor rates, and what to keep.
- [Free Check Engine Code Reading: Parts Stores vs Your Phone](https://derate.app/guides/free-check-engine-code-reading) · ES: [Leer códigos gratis: refaccionaria o tu celular](https://derate.app/guias/free-check-engine-code-reading): Free check engine code reading at AutoZone, O'Reilly and Advance: what they do, what they skip (no Class 8, no clearing), and the phone options for trucks.
- [Freightliner Cascadia Warning Lights: What Each Means](https://derate.app/guides/freightliner-cascadia-warning-lights) · ES: [Testigos del Freightliner Cascadia: qué significa cada uno](https://derate.app/guias/freightliner-cascadia-warning-lights): Freightliner Cascadia warning lights explained: check engine, stop engine, MIL, DPF, HEST, DEF, ABS, coolant, oil and low air, plus how to read SPN/FMI.
- [Low Oil Pressure Warning on a Diesel Truck: Stop or Drive?](https://derate.app/guides/low-oil-pressure-warning-diesel-truck) · ES: [Baja presión de aceite en el tráiler: ¿parar o seguir?](https://derate.app/guias/low-oil-pressure-warning-diesel-truck): Low oil pressure on a diesel truck: normal psi at idle and road speed, causes from low level to worn bearings, the red lamp rule, and tow vs limp costs.
- [NOx Sensor Failure: Symptoms, Codes and Replacement Cost](https://derate.app/guides/nox-sensor-failure-symptoms) · ES: [Falla del sensor de NOx: síntomas, códigos y costo](https://derate.app/guias/nox-sensor-failure-symptoms): NOx sensor failure on a diesel truck: inlet vs outlet, SPN 3216 and 3226, SCR efficiency faults, why they get misdiagnosed, and typical replacement cost.
- [OBD2 Codes Explained: P0, P1, C, B and U Codes](https://derate.app/guides/obd2-codes-explained) · ES: [Códigos OBD2 explicados: P0, P1, C, B y U](https://derate.app/guias/obd2-codes-explained): OBD2 codes explained: the 5-character structure, generic vs manufacturer codes, P0420, P0300, P0171, P0455, P0442, freeze frame and permanent codes.
- [OBD2 Scanner for Semi Trucks: Why Most Don't Work (J1939)](https://derate.app/guides/obd2-scanner-for-semi-trucks) · ES: [Escáner OBD2 para tráiler: por qué casi ninguno sirve](https://derate.app/guias/obd2-scanner-for-semi-trucks): Why a car OBD2 scanner shows nothing on a semi truck: J1939 9-pin vs 16-pin, 250k vs 500k baud, which truck scanners work, and the no-hardware option.
- [PACCAR MX Fault Codes on Peterbilt and Kenworth Trucks](https://derate.app/guides/paccar-mx-fault-codes-peterbilt-kenworth) · ES: [Códigos PACCAR MX en Peterbilt y Kenworth](https://derate.app/guias/paccar-mx-fault-codes-peterbilt-kenworth): PACCAR MX-13 and MX-11 fault codes: P-codes vs SPN/FMI on the dash, common DEF, DPF, EGR, turbo, fuel and coolant codes, derate steps, what to check first.
- [Read a Check Engine Light Without a Scanner or Adapter](https://derate.app/guides/read-check-engine-light-without-scanner) · ES: [Leer el check engine sin escáner ni adaptador](https://derate.app/guias/read-check-engine-light-without-scanner): How to read a truck check engine light without a scanner: SPN/FMI on the dash display, flash codes on older engines, and when the lamp colour decides.
- [Semi Truck Breakdown on the Highway: Step-by-Step Plan](https://derate.app/guides/semi-truck-breakdown-what-to-do) · ES: [Tráiler descompuesto en carretera: plan paso a paso](https://derate.app/guias/semi-truck-breakdown-what-to-do): Semi truck breakdown plan: triangle placement per 49 CFR 392.22, read the code first, who to call in order, Class 8 tow cost ranges, reefer and HOS notes.
- [Semi Truck Overheating: Causes, Codes and What to Do](https://derate.app/guides/semi-truck-overheating-causes) · ES: [Tráiler sobrecalentado: causas, códigos y qué hacer](https://derate.app/guias/semi-truck-overheating-causes): Semi truck overheating: normal temps and warning points, causes from low coolant to EGR cooler, what to do on the road, coolant derate and repair costs.
- [SPN and FMI Fault Codes Explained (J1939 for Trucks)](https://derate.app/guides/spn-fmi-fault-codes-explained) · ES: [Códigos SPN y FMI explicados (J1939 para tráileres)](https://derate.app/guias/spn-fmi-fault-codes-explained): SPN and FMI fault codes explained: what each number means, the FMI list 0-31, occurrence count, active vs inactive, source address and Cummins mapping.
- [Truck Won't Regen: Causes, Checks and When to Stop](https://derate.app/guides/truck-wont-regen) · ES: [El tráiler no hace regeneración: causas y qué revisar](https://derate.app/guias/truck-wont-regen): Why a parked regen won't start on a semi: inhibit switch, coolant temp, active faults, clogged doser, soot level. What to check in the cab and shop costs.
- [Volvo D13 and Mack MP8 Fault Codes: A Driver's Guide](https://derate.app/guides/volvo-mack-fault-codes-guide) · ES: [Códigos Volvo D13 y Mack MP8: guía para el chofer](https://derate.app/guias/volvo-mack-fault-codes-guide): Volvo D13 and Mack MP8 fault codes: MID/PID/FMI vs SPN/FMI on the cluster, DEF, DPF, 7th injector, EGR, turbo and coolant faults, and remote diagnostics.
- [Air Brake Problems and ABS Codes: A Driver's Guide](https://derate.app/guides/air-brake-problems-and-codes) · ES: [Fallas de frenos de aire y códigos ABS: guía para choferes](https://derate.app/guias/air-brake-problems-and-codes): Common air brake problems on semi trucks, the daily air brake check step by step, what the ABS light means, and when brake issues mean stop now.
- [Truck Check Engine Light Colors: Amber vs Red Stop](https://derate.app/guides/check-engine-light-colors-trucks) · ES: [Colores del check engine en tráileres: ámbar vs rojo](https://derate.app/guias/check-engine-light-colors-trucks): Amber check engine, MIL or red stop engine? What each truck warning lamp color means, flashing vs solid, and when you must pull over right away.
- [CVSA Out-of-Service Violations: Top Causes & How to Avoid](https://derate.app/guides/cvsa-out-of-service-violations) · ES: [Fuera de servicio CVSA: frenos y llantas, las más comunes](https://derate.app/guias/cvsa-out-of-service-violations): The most common CVSA out-of-service violations for trucks and drivers, based on 2025 Roadcheck data, and simple habits that keep you rolling.
- [DEF System Problems: Symptoms, Codes & Fixes (2026)](https://derate.app/guides/def-fault-codes-explained) · ES: [Problemas del DEF en camión: síntomas, códigos y solución](https://derate.app/guias/def-fault-codes-explained): Most DEF trouble is low or bad DEF, a failing sensor or a clogged doser. Symptoms, SPN 3364 and other codes, dash warnings, fixes.
- [Diesel Gelling: Winter Tips for Truck Drivers](https://derate.app/guides/diesel-gelling-winter-tips) · ES: [Diésel congelado: tips de invierno para traileros](https://derate.app/guias/diesel-gelling-winter-tips): Why diesel gels in cold weather, the temperatures to watch, how to prevent it with blends and additives, and what to do if your truck's fuel gels.
- [DPF Regeneration Guide: Passive, Active, Parked, Forced](https://derate.app/guides/dpf-regeneration-guide) · ES: [Guía de regeneración del DPF: pasiva, activa y estacionada](https://derate.app/guias/dpf-regeneration-guide): How DPF regeneration works on heavy trucks: passive, active, parked and forced regens, what the DPF and HEST lamps mean, and how to avoid frequent regens.
- [EGR Valve and EGR Cooler Problems: Signs and Causes](https://derate.app/guides/egr-valve-and-cooler-problems) · ES: [Falla del EGR en tu troca: señales de válvula y enfriador](https://derate.app/guias/egr-valve-and-cooler-problems): How to spot EGR valve and cooler problems on a diesel truck: white smoke, coolant loss, black smoke, low power, extra regens, and when to see a mechanic.
- [Owner-Operator Cost Per Mile: Formula, Example, 2025 Data](https://derate.app/guides/owner-operator-cost-per-mile) · ES: [Costo por milla del owner-operator: cómo calcularlo](https://derate.app/guias/owner-operator-cost-per-mile): Cost per mile = yearly costs, including your pay, ÷ total miles. Worked example: $2.368 a mile; ATRI's 2025 fleet average: $2.336.
- [Semi Truck Pre-Trip Inspection Checklist (Step by Step)](https://derate.app/guides/pre-trip-inspection-checklist) · ES: [Checklist de inspección pre-viaje para tráiler, paso a paso](https://derate.app/guias/pre-trip-inspection-checklist): A practical semi truck pre-trip inspection checklist: engine, tires, brakes, lights, coupling and cab, plus what FMCSA rules require before you drive.
- [Turbo Failure Signs on a Semi Truck: What to Watch For](https://derate.app/guides/turbo-failure-signs) · ES: [Turbo dañado en tu tráiler: 10 señales y sus causas](https://derate.app/guias/turbo-failure-signs): Early signs of turbo failure on a semi truck: whining, low boost, smoke, oil use and power loss, plus common causes and how to make your turbo last longer.
- [Truck Derate Mode: Why Your Truck Is Derating (2026)](https://derate.app/guides/what-is-engine-derate) · ES: [Derrateo de motor: por qué tu camión pierde potencia](https://derate.app/guias/what-is-engine-derate): Derate mode is the engine computer cutting power or speed to protect the engine or emissions. Causes, codes, how to get out.

## News

Hubs: https://derate.app/news (EN) · https://derate.app/noticias (ES) — RSS: https://derate.app/news/rss.xml, https://derate.app/noticias/rss.xml

- [Diesel hits $6.276 a gallon, up 9.7 cents (week of Oct. 19)](https://derate.app/news/diesel-price-jumps-week-of-oct-19-2026) · ES: [El diésel sube casi 10 centavos: $6.276 por galón](https://derate.app/noticias/diesel-price-jumps-week-of-oct-19-2026): The EIA national diesel average is $6.276 a gallon for the week of Oct. 19, up 9.7 cents. Every region rose; California tops $8.24.
- [DataQs reform now live in all 50 states](https://derate.app/news/fmcsa-dataqs-reform-all-50-states) · ES: [La reforma de DataQs ya opera en los 50 estados](https://derate.app/noticias/fmcsa-dataqs-reform-all-50-states): FMCSA says every state now uses a three-step DataQs review with set deadlines, so the officer who wrote a violation can't decide its denial alone.
- [EPA 2027 NOx rule: what's set and what may change](https://derate.app/news/epa-2027-nox-rule-status-def-derate-changes) · ES: [Norma EPA 2027 de NOx: qué está firme y qué puede cambiar](https://derate.app/noticias/epa-2027-nox-rule-status-def-derate-changes): The 35 mg low-NOx limit still starts January 2027. EPA's proposed fixes on DEF derates, warranty and penalties are not final yet.
- [I-95 blitz sidelines 78 drivers, 12 over English](https://derate.app/news/i-95-operation-english-proficiency-out-of-service) · ES: [Operativo en la I-95 saca a 78 operadores, 12 por inglés](https://derate.app/noticias/i-95-operation-english-proficiency-out-of-service): A one-day operation in four Southeast states ran 552 inspections. It put 78 drivers and 25 trucks out of service, 12 of them for English proficiency.
- [Cascadia and 49X recalled again over brake valves](https://derate.app/news/freightliner-cascadia-western-star-49x-brake-valve-recall) · ES: [Cascadia y 49X, a revisión otra vez por válvulas de freno](https://derate.app/noticias/freightliner-cascadia-western-star-49x-brake-valve-recall): Daimler is recalling about 2,404 Freightliner Cascadia and Western Star 49X trucks that were repaired the wrong way under earlier brake modulator recalls.
- [Laredo stays tight as Mexico exports hit a record](https://derate.app/news/laredo-cross-border-capacity-saturday-hours-pilot) · ES: [Laredo sigue apretado y México marca récord de exportaciones](https://derate.app/noticias/laredo-cross-border-capacity-saturday-hours-pilot): Mexican exports to the U.S. set a first-half record, Laredo capacity is tight, and a pilot keeps the World Trade Bridge open later on Saturdays.

## MCP Server

Public, read-only Model Context Protocol server. No authentication.

- Endpoint: https://derate.app/mcp (Streamable HTTP, JSON-RPC 2.0 over POST; protocolVersion 2025-06-18 by default)
- Descriptor: https://derate.app/.well-known/mcp.json
- Registry entry: https://derate.app/server.json (also https://derate.app/.well-known/mcp/server.json)
- Read-only tools: `buscar_codigo`, `es_seguro_manejar`, `retiros_de_camion`, `get_data_notes`, `search_guides`, `get_guide` (lang 'en' | 'es'); every result carries a derate.app URL to cite.

- `get_truck_fault_code`: Look up a diesel truck fault code (J1939 SPN/FMI such as 'SPN 3251 FMI 0', or an OBD-II code such as 'P2002') in DERATE's public fault-code library. Returns what the code means, its severity, whether it is safe to keep driving, probable causes, the recommended tests, and the canonical URL of the public page for that code. Works without any account.
- `interpret_derate`: Explain a diesel truck engine derate or power-loss symptom described in plain language (for example 'DEF light on and truck limited to 55 mph'). Returns the most likely cause, how urgent it is, the immediate action to take, and matching public fault-code pages. This is the free public interpretation; the full guided diagnosis with tests and a work order runs in the DERATE app.
- `search_fault_code_library`: Full-text search over DERATE's public diesel truck fault-code library by code, system, dashboard light or symptom words. Returns a list of matching entries with code, title, severity, system and the canonical public URL.
- `list_supported_engine_families`: List the diesel truck engine families and code protocols DERATE interprets (J1939 SPN/FMI and OBD-II), so an agent knows whether a given truck is covered before looking up a code.
- `get_pricing`: List DERATE's plans and prices in USD. The app is a free download; plans are purchased inside the iOS/Android app (App Store / Google Play). Monthly Driver and Shop plans include a 7-day free trial for new subscribers.
- `get_download_links`: Return the official App Store and Google Play links for the DERATE native app (iOS and Android). DERATE runs only as a mobile app.

Browser agents on the download page also get WebMCP tools (navigator.modelContext): buscar_codigo, es_seguro_manejar, retiros_de_camion, get_data_notes, search_guides, get_guide.

## Frequently asked

- What is an engine derate? A power or speed reduction commanded by the engine ECM after a fault (commonly DEF/SCR, DPF, or aftertreatment) to protect the engine and force repair; it escalates in stages down to a 5 mph limp mode.
- Can DERATE read codes without an OBD scanner? Yes — the app reads the codes from a photo of the instrument cluster or of a scanner screen; no hardware dongle is required.
- Does it replace a technician? No. It gives an objective diagnosis, an ordered test plan, and a work order; a qualified technician performs the repair.

## Fault codes (Spanish)

- [P0299 — Turbo con poca presión](https://derate.app/codigo/p0299): El turbo no da la presión que pide el motor. Severidad: YELLOW. Sistema: Admisión / Turbo. Pieza que se suele cambiar: Actuador del turbo (VGT) ($600–$2200 USD).
- [SPN 102 FMI 18 — Presión del turbo](https://derate.app/codigo/spn-102-fmi-18): La presión del múltiple de admisión está baja: falta fuerza. Severidad: YELLOW. Sistema: Admisión / Turbo. Pieza que se suele cambiar: Sensor de presión de turbo (boost) ($60–$260 USD).
- [SPN 105 — Temperatura del múltiple de admisión](https://derate.app/codigo/spn-105): El módulo de control del camión (ECU) reporta una falla en: Temperatura del múltiple de admisión. Severidad: YELLOW. Sistema: Admisión / Turbo. Pieza que se suele cambiar: Sensor de temperatura del múltiple de admisión ($40–$180 USD).
- [SPN 641 — Actuador del turbo (VGT)](https://derate.app/codigo/spn-641): El módulo de control del camión (ECU) reporta una falla en: Actuador del turbo (VGT). Severidad: YELLOW. Sistema: Admisión / Turbo. Pieza que se suele cambiar: Actuador del turbo (VGT) ($600–$2200 USD).
- [SPN 171 — Temperatura del aire ambiente](https://derate.app/codigo/spn-171): El módulo de control del camión (ECU) reporta una falla en: Temperatura del aire ambiente. Severidad: WHITE. Sistema: Ambiente. Pieza que se suele cambiar: Sensor de temperatura ambiente ($25–$120 USD).
- [SPN 441 — Temperatura auxiliar](https://derate.app/codigo/spn-441): El módulo de control del camión (ECU) reporta una falla en: Temperatura auxiliar. Severidad: WHITE. Sistema: Auxiliar.
- [SPN 84 — Velocidad del vehículo por ruedas](https://derate.app/codigo/spn-84): El módulo de control del camión (ECU) reporta una falla en: Velocidad del vehículo por ruedas. Severidad: YELLOW. Sistema: Chasis. Pieza que se suele cambiar: Sensor de velocidad de rueda ($40–$180 USD).
- [P0088 — Presión del riel demasiado alta](https://derate.app/codigo/p0088): El módulo de control del camión (ECU) reporta una falla en: Presión del riel demasiado alta. Severidad: RED. Sistema: Combustible. Pieza que se suele cambiar: Regulador / válvula de alivio de presión de combustible ($150–$600 USD).
- [SPN 94 — Presión de entrega de combustible](https://derate.app/codigo/spn-94): El módulo de control del camión (ECU) reporta una falla en: Presión de entrega de combustible. Severidad: YELLOW. Sistema: Combustible. Pieza que se suele cambiar: Filtros de combustible (primario y secundario) ($40–$160 USD).
- [SPN 97 — Agua en el combustible](https://derate.app/codigo/spn-97): El módulo de control del camión (ECU) reporta una falla en: Agua en el combustible. Severidad: WHITE. Sistema: Combustible. Pieza que se suele cambiar: Filtro separador de agua ($30–$120 USD).
- [SPN 157 — Presión del riel de inyectores](https://derate.app/codigo/spn-157): El módulo de control del camión (ECU) reporta una falla en: Presión del riel de inyectores. Severidad: YELLOW. Sistema: Combustible. Pieza que se suele cambiar: Sensor de presión del riel de combustible ($120–$450 USD).
- [SPN 651 — Inyector del cilindro 1](https://derate.app/codigo/spn-651): El módulo de control del camión (ECU) reporta una falla en: Inyector del cilindro 1. Severidad: YELLOW. Sistema: Combustible. Pieza que se suele cambiar: Inyector (uno) ($350–$1200 USD).
- [P0401 — Flujo de EGR insuficiente](https://derate.app/codigo/p0401): El módulo de control del camión (ECU) reporta una falla en: Flujo de EGR insuficiente. Severidad: YELLOW. Sistema: EGR. Pieza que se suele cambiar: Válvula EGR ($350–$1400 USD).
- [SPN 27 — Posición de la válvula EGR](https://derate.app/codigo/spn-27): El módulo de control del camión (ECU) reporta una falla en: Posición de la válvula EGR. Severidad: YELLOW. Sistema: EGR. Pieza que se suele cambiar: Válvula EGR ($350–$1400 USD).
- [SPN 411 — Presión diferencial EGR](https://derate.app/codigo/spn-411): El módulo de control del camión (ECU) reporta una falla en: Presión diferencial EGR. Severidad: YELLOW. Sistema: EGR. Pieza que se suele cambiar: Sensor de presión diferencial EGR ($90–$320 USD).
- [SPN 412 — Temperatura EGR](https://derate.app/codigo/spn-412): El módulo de control del camión (ECU) reporta una falla en: Temperatura EGR. Severidad: YELLOW. Sistema: EGR. Pieza que se suele cambiar: Sensor de temperatura EGR ($60–$220 USD).
- [SPN 2791 — Control de la válvula EGR](https://derate.app/codigo/spn-2791): El módulo de control del camión (ECU) reporta una falla en: Control de la válvula EGR. Severidad: YELLOW. Sistema: EGR. Pieza que se suele cambiar: Válvula EGR ($350–$1400 USD).
- [P0562 — Voltaje del sistema bajo](https://derate.app/codigo/p0562): El módulo de control del camión (ECU) reporta una falla en: Voltaje del sistema bajo. Severidad: YELLOW. Sistema: Eléctrico / J1939. Pieza que se suele cambiar: Alternador ($300–$1200 USD).
- [SPN 168 — Voltaje de batería / carga](https://derate.app/codigo/spn-168): El módulo de control del camión (ECU) reporta una falla en: Voltaje de batería / carga. Severidad: YELLOW. Sistema: Eléctrico / J1939. Pieza que se suele cambiar: Alternador ($300–$1200 USD).
- [SPN 620 — Alimentación de 5V a sensores](https://derate.app/codigo/spn-620): El módulo de control del camión (ECU) reporta una falla en: Alimentación de 5V a sensores. Severidad: YELLOW. Sistema: Eléctrico / J1939. Pieza que se suele cambiar: Reparación de arnés / alimentación de sensores ($40–$400 USD).
- [SPN 627 — Alimentación eléctrica de la ECU](https://derate.app/codigo/spn-627): El módulo de control del camión (ECU) reporta una falla en: Alimentación eléctrica de la ECU. Severidad: YELLOW. Sistema: Eléctrico / J1939. Pieza que se suele cambiar: Reparación del circuito de alimentación del ECM ($40–$500 USD).
- [SPN 639 FMI 2 — Bus de datos](https://derate.app/codigo/spn-639-fmi-2): La red del camión pierde comunicación entre módulos. Severidad: YELLOW. Sistema: Eléctrico / J1939. Pieza que se suele cambiar: Reparación de la red J1939 (conector / resistencia terminal) ($20–$350 USD).
- [SPN 1231 — Red de datos J1939-1](https://derate.app/codigo/spn-1231): El módulo de control del camión (ECU) reporta una falla en: Red de datos J1939-1. Severidad: YELLOW. Sistema: Eléctrico / J1939. Pieza que se suele cambiar: Reparación de la red J1939 (conector / resistencia terminal) ($20–$350 USD).
- [SPN 2003 — Red de datos de la transmisión](https://derate.app/codigo/spn-2003): El módulo de control del camión (ECU) reporta una falla en: Red de datos de la transmisión. Severidad: YELLOW. Sistema: Eléctrico / J1939. Pieza que se suele cambiar: Arnés / conector de transmisión ($80–$600 USD).
- [P0128 — Termostato por debajo de la temperatura de trabajo](https://derate.app/codigo/p0128): El módulo de control del camión (ECU) reporta una falla en: Termostato por debajo de la temperatura de trabajo. Severidad: WHITE. Sistema: Enfriamiento. Pieza que se suele cambiar: Termostato ($60–$320 USD).
- [SPN 110 FMI 0 — Temperatura alta](https://derate.app/codigo/spn-110-fmi-0): El refrigerante está muy caliente: riesgo de daño al motor. Severidad: RED. Sistema: Enfriamiento. Pieza que se suele cambiar: Sensor de temperatura de refrigerante ($40–$180 USD).
- [SPN 111 — Nivel de refrigerante](https://derate.app/codigo/spn-111): El módulo de control del camión (ECU) reporta una falla en: Nivel de refrigerante. Severidad: YELLOW. Sistema: Enfriamiento. Pieza que se suele cambiar: Sensor de nivel de refrigerante ($40–$200 USD).
- [SPN 597 — Interruptor del freno](https://derate.app/codigo/spn-597): El módulo de control del camión (ECU) reporta una falla en: Interruptor del freno. Severidad: RED. Sistema: Frenos / ABS. Pieza que se suele cambiar: Interruptor del pedal de freno ($25–$140 USD).
- [SPN 598 — Interruptor del clutch](https://derate.app/codigo/spn-598): El módulo de control del camión (ECU) reporta una falla en: Interruptor del clutch. Severidad: YELLOW. Sistema: Frenos / ABS. Pieza que se suele cambiar: Interruptor del pedal de clutch ($25–$140 USD).
- [SPN 789 FMI 7 — ABS del tráiler](https://derate.app/codigo/spn-789-fmi-7): El ABS quedó desactivado: los frenos siguen, la asistencia no. Severidad: RED. Sistema: Frenos / ABS.
- [SPN 1067 — Evento de ABS](https://derate.app/codigo/spn-1067): El módulo de control del camión (ECU) reporta una falla en: Evento de ABS. Severidad: RED. Sistema: Frenos / ABS. Pieza que se suele cambiar: Modulador / módulo ABS ($250–$1500 USD).
- [SPN 100 FMI 1 — Presión de aceite](https://derate.app/codigo/spn-100-fmi-1): La presión de aceite está muy baja: para el motor ya. Severidad: RED. Sistema: Lubricación. Pieza que se suele cambiar: Sensor de presión de aceite ($50–$240 USD).
- [SPN 51 — Posición del acelerador (mariposa)](https://derate.app/codigo/spn-51): El módulo de control del camión (ECU) reporta una falla en: Posición del acelerador (mariposa). Severidad: YELLOW. Sistema: Motor. Pieza que se suele cambiar: Sensor de posición del acelerador ($80–$350 USD).
- [SPN 91 — Posición del pedal del acelerador](https://derate.app/codigo/spn-91): El módulo de control del camión (ECU) reporta una falla en: Posición del pedal del acelerador. Severidad: YELLOW. Sistema: Motor. Pieza que se suele cambiar: Pedal del acelerador (conjunto) ($180–$650 USD).
- [SPN 98 — Nivel de aceite del motor](https://derate.app/codigo/spn-98): El módulo de control del camión (ECU) reporta una falla en: Nivel de aceite del motor. Severidad: YELLOW. Sistema: Motor. Pieza que se suele cambiar: Sensor de nivel de aceite ($60–$260 USD).
- [SPN 190 — Velocidad del motor (RPM)](https://derate.app/codigo/spn-190): El módulo de control del camión (ECU) reporta una falla en: Velocidad del motor (RPM). Severidad: YELLOW. Sistema: Motor. Pieza que se suele cambiar: Sensor de posición del cigüeñal ($60–$280 USD).
- [SPN 512 — Par solicitado por el chofer](https://derate.app/codigo/spn-512): El módulo de control del camión (ECU) reporta una falla en: Par solicitado por el chofer. Severidad: WHITE. Sistema: Motor.
- [SPN 1569 FMI 31 — Derate de par](https://derate.app/codigo/spn-1569-fmi-31): El motor está limitando la fuerza a propósito. Severidad: RED. Sistema: Motor.
- [P2002 — Eficiencia del filtro DPF bajo el límite](https://derate.app/codigo/p2002): El módulo de control del camión (ECU) reporta una falla en: Eficiencia del filtro DPF bajo el límite. Severidad: YELLOW. Sistema: Postratamiento / DPF. Pieza que se suele cambiar: Limpieza del DPF (o filtro nuevo si está dañado) ($400–$4500 USD).
- [SPN 3242 — Temperatura de entrada del filtro DPF](https://derate.app/codigo/spn-3242): El módulo de control del camión (ECU) reporta una falla en: Temperatura de entrada del filtro DPF. Severidad: YELLOW. Sistema: Postratamiento / DPF. Pieza que se suele cambiar: Sensor de temperatura del DPF ($90–$350 USD).
- [SPN 3246 — Temperatura de salida del filtro DPF](https://derate.app/codigo/spn-3246): El módulo de control del camión (ECU) reporta una falla en: Temperatura de salida del filtro DPF. Severidad: YELLOW. Sistema: Postratamiento / DPF. Pieza que se suele cambiar: Sensor de temperatura del DPF ($90–$350 USD).
- [SPN 3251 FMI 0 — Filtro de partículas](https://derate.app/codigo/spn-3251-fmi-0): El filtro de partículas está tapado y el motor pierde fuerza. Severidad: YELLOW. Sistema: Postratamiento / DPF. Pieza que se suele cambiar: Sensor de presión diferencial del DPF ($180–$420 USD).
- [SPN 3719 — Carga de hollín del filtro DPF](https://derate.app/codigo/spn-3719): El módulo de control del camión (ECU) reporta una falla en: Carga de hollín del filtro DPF. Severidad: YELLOW. Sistema: Postratamiento / DPF. Pieza que se suele cambiar: Limpieza del DPF (o filtro nuevo si está dañado) ($400–$4500 USD).
- [P20EE — Eficiencia del SCR bajo el límite](https://derate.app/codigo/p20ee): El módulo de control del camión (ECU) reporta una falla en: Eficiencia del SCR bajo el límite. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Catalizador SCR ($1500–$6000 USD).
- [P20EF — Eficiencia del precatalizador SCR de NOx bajo el límite (Banco 1)](https://derate.app/codigo/p20ef): El módulo de control del camión (ECU) reporta una falla en: Eficiencia del precatalizador SCR de NOx bajo el límite (Banco 1). Severidad: YELLOW. Sistema: SCR / DEF.
- [SPN 3055 — NOx de entrada del postratamiento](https://derate.app/codigo/spn-3055): El módulo de control del camión (ECU) reporta una falla en: NOx de entrada del postratamiento. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Sensor NOx de entrada (salida de motor) ($280–$800 USD).
- [SPN 3216 — Sensor NOx de entrada del SCR](https://derate.app/codigo/spn-3216): El módulo de control del camión (ECU) reporta una falla en: Sensor NOx de entrada del SCR. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Sensor NOx de entrada (salida de motor) ($280–$800 USD).
- [SPN 3226 — Sensor NOx de salida del SCR](https://derate.app/codigo/spn-3226): El módulo de control del camión (ECU) reporta una falla en: Sensor NOx de salida del SCR. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Sensor NOx de salida (escape) ($280–$800 USD).
- [SPN 3361 — Unidad dosificadora de DEF](https://derate.app/codigo/spn-3361): El módulo de control del camión (ECU) reporta una falla en: Unidad dosificadora de DEF. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Módulo dosificador de DEF (bomba) ($700–$2800 USD).
- [SPN 3364 FMI 18 — Calidad de DEF](https://derate.app/codigo/spn-3364-fmi-18): El sistema detectó DEF fuera de especificación. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Vaciar y rellenar tanque de DEF (fluido contaminado) ($80–$350 USD).
- [SPN 3516 — Concentración del DEF](https://derate.app/codigo/spn-3516): El módulo de control del camión (ECU) reporta una falla en: Concentración del DEF. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Sensor de calidad / nivel de DEF (cabezal del tanque) ($350–$1400 USD).
- [SPN 4094 — Límites de NOx excedidos — derate](https://derate.app/codigo/spn-4094): El módulo de control del camión (ECU) reporta una falla en: Límites de NOx excedidos — derate. Severidad: RED. Sistema: SCR / DEF. Pieza que se suele cambiar: Sensor NOx de salida (escape) ($280–$800 USD).
- [SPN 4364 — Eficiencia de conversión del SCR](https://derate.app/codigo/spn-4364): El módulo de control del camión (ECU) reporta una falla en: Eficiencia de conversión del SCR. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Catalizador SCR ($1500–$6000 USD).
- [SPN 5246 FMI 0 — Inducción de DEF](https://derate.app/codigo/spn-5246-fmi-0): El sistema de DEF activó el derate: la velocidad se va a limitar. Severidad: RED. Sistema: SCR / DEF. Pieza que se suele cambiar: Regeneración forzada (en taller) ($150–$500 USD).
- [SPN 5394 — Válvula dosificadora de DEF](https://derate.app/codigo/spn-5394): El módulo de control del camión (ECU) reporta una falla en: Válvula dosificadora de DEF. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Válvula dosificadora / inyector de DEF ($250–$900 USD).
- [SPN 5571 — Alivio de alta presión de DEF](https://derate.app/codigo/spn-5571): El módulo de control del camión (ECU) reporta una falla en: Alivio de alta presión de DEF. Severidad: YELLOW. Sistema: SCR / DEF. Pieza que se suele cambiar: Línea de presión / válvula de alivio de DEF ($120–$600 USD).
- [SPN 560 — Tren motriz de la transmisión acoplado](https://derate.app/codigo/spn-560): El módulo de control del camión (ECU) reporta una falla en: Tren motriz de la transmisión acoplado. Severidad: YELLOW. Sistema: Transmisión. Pieza que se suele cambiar: Arnés / conector de transmisión ($80–$600 USD).

## Fault codes (English)

- [P2002 — DPF efficiency below threshold](https://derate.app/code/p2002): The truck's control module (ECU) reports a fault on: DPF efficiency below threshold. Severity: YELLOW. System: Aftertreatment / DPF. Part usually replaced: DPF cleaning (or filter if cracked) ($400–$4500 USD).
- [SPN 3242 — DPF intake temperature](https://derate.app/code/spn-3242): The truck's control module (ECU) reports a fault on: DPF intake temperature. Severity: YELLOW. System: Aftertreatment / DPF. Part usually replaced: DPF temperature sensor ($90–$350 USD).
- [SPN 3246 — DPF outlet temperature](https://derate.app/code/spn-3246): The truck's control module (ECU) reports a fault on: DPF outlet temperature. Severity: YELLOW. System: Aftertreatment / DPF. Part usually replaced: DPF temperature sensor ($90–$350 USD).
- [SPN 3251 FMI 0 — Particulate filter](https://derate.app/code/spn-3251-fmi-0): The particulate filter is plugged and the engine is losing power. Severity: YELLOW. System: Aftertreatment / DPF. Part usually replaced: DPF differential pressure sensor ($180–$420 USD).
- [SPN 3719 — DPF soot load](https://derate.app/code/spn-3719): The truck's control module (ECU) reports a fault on: DPF soot load. Severity: YELLOW. System: Aftertreatment / DPF. Part usually replaced: DPF cleaning (or filter if cracked) ($400–$4500 USD).
- [P0299 — Turbo underboost](https://derate.app/code/p0299): The turbo is not making the boost the engine asks for. Severity: YELLOW. System: Air intake / Turbo. Part usually replaced: Turbo (VGT) actuator ($600–$2200 USD).
- [SPN 102 FMI 18 — Boost pressure](https://derate.app/code/spn-102-fmi-18): Intake manifold pressure is low: the truck is down on power. Severity: YELLOW. System: Air intake / Turbo. Part usually replaced: Boost pressure sensor ($60–$260 USD).
- [SPN 105 — Intake manifold temperature](https://derate.app/code/spn-105): The truck's control module (ECU) reports a fault on: Intake manifold temperature. Severity: YELLOW. System: Air intake / Turbo. Part usually replaced: Intake manifold temperature sensor ($40–$180 USD).
- [SPN 641 — Turbo actuator (VGT)](https://derate.app/code/spn-641): The truck's control module (ECU) reports a fault on: Turbo actuator (VGT). Severity: YELLOW. System: Air intake / Turbo. Part usually replaced: Turbo (VGT) actuator ($600–$2200 USD).
- [SPN 171 — Ambient air temperature](https://derate.app/code/spn-171): The truck's control module (ECU) reports a fault on: Ambient air temperature. Severity: WHITE. System: Ambient. Part usually replaced: Ambient air temperature sensor ($25–$120 USD).
- [SPN 441 — Auxiliary temperature](https://derate.app/code/spn-441): The truck's control module (ECU) reports a fault on: Auxiliary temperature. Severity: WHITE. System: Auxiliary.
- [SPN 597 — Brake switch](https://derate.app/code/spn-597): The truck's control module (ECU) reports a fault on: Brake switch. Severity: RED. System: Brakes / ABS. Part usually replaced: Brake light / pedal switch ($25–$140 USD).
- [SPN 598 — Clutch switch](https://derate.app/code/spn-598): The truck's control module (ECU) reports a fault on: Clutch switch. Severity: YELLOW. System: Brakes / ABS. Part usually replaced: Clutch pedal switch ($25–$140 USD).
- [SPN 789 FMI 7 — Trailer ABS](https://derate.app/code/spn-789-fmi-7): ABS is disabled: the brakes still work, the assist does not. Severity: RED. System: Brakes / ABS.
- [SPN 1067 — ABS event](https://derate.app/code/spn-1067): The truck's control module (ECU) reports a fault on: ABS event. Severity: RED. System: Brakes / ABS. Part usually replaced: ABS modulator valve / ECU ($250–$1500 USD).
- [SPN 84 — Wheel-based vehicle speed](https://derate.app/code/spn-84): The truck's control module (ECU) reports a fault on: Wheel-based vehicle speed. Severity: YELLOW. System: Chassis. Part usually replaced: Wheel speed sensor ($40–$180 USD).
- [P0128 — Thermostat below regulating temp](https://derate.app/code/p0128): The truck's control module (ECU) reports a fault on: Thermostat below regulating temp. Severity: WHITE. System: Cooling. Part usually replaced: Thermostat ($60–$320 USD).
- [SPN 110 FMI 0 — High temperature](https://derate.app/code/spn-110-fmi-0): Coolant is running too hot: engine damage risk. Severity: RED. System: Cooling. Part usually replaced: Coolant temperature sensor ($40–$180 USD).
- [SPN 111 — Coolant level](https://derate.app/code/spn-111): The truck's control module (ECU) reports a fault on: Coolant level. Severity: YELLOW. System: Cooling. Part usually replaced: Coolant level sensor ($40–$200 USD).
- [P0401 — EGR flow insufficient](https://derate.app/code/p0401): The truck's control module (ECU) reports a fault on: EGR flow insufficient. Severity: YELLOW. System: EGR. Part usually replaced: EGR valve ($350–$1400 USD).
- [SPN 27 — EGR valve position](https://derate.app/code/spn-27): The truck's control module (ECU) reports a fault on: EGR valve position. Severity: YELLOW. System: EGR. Part usually replaced: EGR valve ($350–$1400 USD).
- [SPN 411 — EGR differential pressure](https://derate.app/code/spn-411): The truck's control module (ECU) reports a fault on: EGR differential pressure. Severity: YELLOW. System: EGR. Part usually replaced: EGR differential pressure sensor ($90–$320 USD).
- [SPN 412 — EGR temperature](https://derate.app/code/spn-412): The truck's control module (ECU) reports a fault on: EGR temperature. Severity: YELLOW. System: EGR. Part usually replaced: EGR temperature sensor ($60–$220 USD).
- [SPN 2791 — EGR valve control](https://derate.app/code/spn-2791): The truck's control module (ECU) reports a fault on: EGR valve control. Severity: YELLOW. System: EGR. Part usually replaced: EGR valve ($350–$1400 USD).
- [P0562 — System voltage low](https://derate.app/code/p0562): The truck's control module (ECU) reports a fault on: System voltage low. Severity: YELLOW. System: Electrical / J1939. Part usually replaced: Alternator ($300–$1200 USD).
- [SPN 168 — Battery / charging voltage](https://derate.app/code/spn-168): The truck's control module (ECU) reports a fault on: Battery / charging voltage. Severity: YELLOW. System: Electrical / J1939. Part usually replaced: Alternator ($300–$1200 USD).
- [SPN 620 — 5V sensor supply](https://derate.app/code/spn-620): The truck's control module (ECU) reports a fault on: 5V sensor supply. Severity: YELLOW. System: Electrical / J1939. Part usually replaced: Sensor supply wiring / harness repair ($40–$400 USD).
- [SPN 627 — ECU power supply](https://derate.app/code/spn-627): The truck's control module (ECU) reports a fault on: ECU power supply. Severity: YELLOW. System: Electrical / J1939. Part usually replaced: ECM power / ground circuit repair ($40–$500 USD).
- [SPN 639 FMI 2 — Data bus](https://derate.app/code/spn-639-fmi-2): The truck network is losing communication between modules. Severity: YELLOW. System: Electrical / J1939. Part usually replaced: J1939 datalink repair (connector / terminating resistor) ($20–$350 USD).
- [SPN 1231 — J1939-1 datalink](https://derate.app/code/spn-1231): The truck's control module (ECU) reports a fault on: J1939-1 datalink. Severity: YELLOW. System: Electrical / J1939. Part usually replaced: J1939 datalink repair (connector / terminating resistor) ($20–$350 USD).
- [SPN 2003 — Transmission datalink](https://derate.app/code/spn-2003): The truck's control module (ECU) reports a fault on: Transmission datalink. Severity: YELLOW. System: Electrical / J1939. Part usually replaced: Transmission harness / connector ($80–$600 USD).
- [SPN 51 — Throttle position](https://derate.app/code/spn-51): The truck's control module (ECU) reports a fault on: Throttle position. Severity: YELLOW. System: Engine. Part usually replaced: Throttle position sensor ($80–$350 USD).
- [SPN 91 — Accelerator pedal position](https://derate.app/code/spn-91): The truck's control module (ECU) reports a fault on: Accelerator pedal position. Severity: YELLOW. System: Engine. Part usually replaced: Accelerator pedal assembly ($180–$650 USD).
- [SPN 98 — Engine oil level](https://derate.app/code/spn-98): The truck's control module (ECU) reports a fault on: Engine oil level. Severity: YELLOW. System: Engine. Part usually replaced: Oil level sensor ($60–$260 USD).
- [SPN 190 — Engine speed](https://derate.app/code/spn-190): The truck's control module (ECU) reports a fault on: Engine speed. Severity: YELLOW. System: Engine. Part usually replaced: Crankshaft position sensor ($60–$280 USD).
- [SPN 512 — Driver's demand torque](https://derate.app/code/spn-512): The truck's control module (ECU) reports a fault on: Driver's demand torque. Severity: WHITE. System: Engine.
- [SPN 1569 FMI 31 — Torque derate](https://derate.app/code/spn-1569-fmi-31): The engine is deliberately limiting power. Severity: RED. System: Engine.
- [P0088 — Rail pressure too high](https://derate.app/code/p0088): The truck's control module (ECU) reports a fault on: Rail pressure too high. Severity: RED. System: Fuel. Part usually replaced: Fuel pressure regulator / relief valve ($150–$600 USD).
- [SPN 94 — Fuel delivery pressure](https://derate.app/code/spn-94): The truck's control module (ECU) reports a fault on: Fuel delivery pressure. Severity: YELLOW. System: Fuel. Part usually replaced: Fuel filter (primary + secondary) ($40–$160 USD).
- [SPN 97 — Water in fuel](https://derate.app/code/spn-97): The truck's control module (ECU) reports a fault on: Water in fuel. Severity: WHITE. System: Fuel. Part usually replaced: Water separator filter ($30–$120 USD).
- [SPN 157 — Injector rail pressure](https://derate.app/code/spn-157): The truck's control module (ECU) reports a fault on: Injector rail pressure. Severity: YELLOW. System: Fuel. Part usually replaced: Fuel rail pressure sensor ($120–$450 USD).
- [SPN 651 — Injector cylinder 1](https://derate.app/code/spn-651): The truck's control module (ECU) reports a fault on: Injector cylinder 1. Severity: YELLOW. System: Fuel. Part usually replaced: Fuel injector (one) ($350–$1200 USD).
- [SPN 100 FMI 1 — Oil pressure](https://derate.app/code/spn-100-fmi-1): Oil pressure is critically low: shut the engine down. Severity: RED. System: Lubrication. Part usually replaced: Oil pressure sensor ($50–$240 USD).
- [P20EE — SCR efficiency below threshold](https://derate.app/code/p20ee): The truck's control module (ECU) reports a fault on: SCR efficiency below threshold. Severity: YELLOW. System: SCR / DEF. Part usually replaced: SCR catalyst ($1500–$6000 USD).
- [P20EF — SCR NOx pre-catalyst efficiency below threshold (Bank 1)](https://derate.app/code/p20ef): The truck's control module (ECU) reports a fault on: SCR NOx pre-catalyst efficiency below threshold (Bank 1). Severity: YELLOW. System: SCR / DEF.
- [SPN 3055 — Aftertreatment intake NOx](https://derate.app/code/spn-3055): The truck's control module (ECU) reports a fault on: Aftertreatment intake NOx. Severity: YELLOW. System: SCR / DEF. Part usually replaced: NOx sensor (inlet / engine-out) ($280–$800 USD).
- [SPN 3216 — SCR intake NOx sensor](https://derate.app/code/spn-3216): The truck's control module (ECU) reports a fault on: SCR intake NOx sensor. Severity: YELLOW. System: SCR / DEF. Part usually replaced: NOx sensor (inlet / engine-out) ($280–$800 USD).
- [SPN 3226 — SCR outlet NOx sensor](https://derate.app/code/spn-3226): The truck's control module (ECU) reports a fault on: SCR outlet NOx sensor. Severity: YELLOW. System: SCR / DEF. Part usually replaced: NOx sensor (outlet / tailpipe) ($280–$800 USD).
- [SPN 3361 — DEF dosing unit](https://derate.app/code/spn-3361): The truck's control module (ECU) reports a fault on: DEF dosing unit. Severity: YELLOW. System: SCR / DEF. Part usually replaced: DEF dosing unit (pump / supply module) ($700–$2800 USD).
- [SPN 3364 FMI 18 — DEF quality](https://derate.app/code/spn-3364-fmi-18): The system detected DEF that is out of specification. Severity: YELLOW. System: SCR / DEF. Part usually replaced: DEF tank drain & refill (contaminated fluid) ($80–$350 USD).
- [SPN 3516 — DEF concentration](https://derate.app/code/spn-3516): The truck's control module (ECU) reports a fault on: DEF concentration. Severity: YELLOW. System: SCR / DEF. Part usually replaced: DEF quality / level sensor (tank header) ($350–$1400 USD).
- [SPN 4094 — NOx limits exceeded — derate](https://derate.app/code/spn-4094): The truck's control module (ECU) reports a fault on: NOx limits exceeded — derate. Severity: RED. System: SCR / DEF. Part usually replaced: NOx sensor (outlet / tailpipe) ($280–$800 USD).
- [SPN 4364 — SCR conversion efficiency](https://derate.app/code/spn-4364): The truck's control module (ECU) reports a fault on: SCR conversion efficiency. Severity: YELLOW. System: SCR / DEF. Part usually replaced: SCR catalyst ($1500–$6000 USD).
- [SPN 5246 FMI 0 — DEF inducement](https://derate.app/code/spn-5246-fmi-0): The DEF system triggered the derate: road speed is about to be limited. Severity: RED. System: SCR / DEF. Part usually replaced: Forced regeneration (shop) ($150–$500 USD).
- [SPN 5394 — DEF dosing valve](https://derate.app/code/spn-5394): The truck's control module (ECU) reports a fault on: DEF dosing valve. Severity: YELLOW. System: SCR / DEF. Part usually replaced: DEF dosing valve / injector ($250–$900 USD).
- [SPN 5571 — DEF high pressure relief](https://derate.app/code/spn-5571): The truck's control module (ECU) reports a fault on: DEF high pressure relief. Severity: YELLOW. System: SCR / DEF. Part usually replaced: DEF pressure line / relief valve ($120–$600 USD).
- [SPN 560 — Transmission driveline engaged](https://derate.app/code/spn-560): The truck's control module (ECU) reports a fault on: Transmission driveline engaged. Severity: YELLOW. System: Transmission. Part usually replaced: Transmission harness / connector ($80–$600 USD).

## Citation

When quoting DERATE, cite the specific code page URL above and keep the severity wording intact: severity drives whether a driver keeps rolling or parks the truck.