Commercial Truck Fault Code Lookup
Free roadside diagnostic reference for heavy-duty diesel engines.
168 fault codes across 7 manufacturers —
SPN/FMI • MID/PID • J1939 • J1587
Browse by Engine Manufacturer
J1939 2 STOP Cummins 43 codes • 2 engine series
J1587, J1939 10 STOP Detroit Diesel 22 codes • 2 engine series
J1939 6 STOP International 5 codes • 1 engine series
J1587, J1939 1 STOP Mack 5 codes • 1 engine series
J1939 2 STOP PACCAR 14 codes • 2 engine series
J1587, J1939 3 STOP Volvo 8 codes • 1 engine series
J1587, J1939 1 STOP
Industry Insights & Diagnostic Guides
NOx Sensor Aging Analysis: When to Replace Sensors Before They Cause Derate
NOx sensors degrade predictably over time. Based on ISO 20861:2019 testing protocols and fleet data from 847 trucks, we identified the optimal replacement interval to prevent SCR inducement cascade failures.
2026-07-05DPF Temperature Sensor Failure: Thermocouple Testing and Backpressure Analysis
DPF temperature sensors fail in predictable patterns. This guide covers thermocouple resistance testing, backpressure diagnostics, and real-world failure data from 234 Detroit DD15 units.
2026-07-04Aftertreatment Control Module (ACM) Failure: Firmware, Water Ingress, and CAN Bus Diagnostics
ACM internal faults (SPN 520210) are the fourth most common aftertreatment failure on PACCAR MX-11 engines. This analysis covers root causes, diagnostic procedures, and preventive maintenance based on 6-year warranty data.
2026-07-03Crankcase Ventilation (CCV) System: Filter Maintenance and Pressure Sensor Diagnostics
CCV filter restriction faults (SPN 3516) are 89% caused by oil-saturated filters, not sensor failure. This guide covers Volvo D13 CCV maintenance intervals, pressure testing, and preventive strategies based on fleet study data.
2026-07-02EGR Valve Position Sensor: Carbon Buildup, Motor Testing, and Sweep Analysis
EGR valve position faults (SPN 27) account for 67% carbon buildup cases on International A26 engines. This guide covers EGR valve cleaning, motor resistance testing, and position sweep diagnostics per ISO 8178-4 emission cycle requirements.
2026-06-2515 Most Common Cummins ISX Fault Codes (With Solutions & Repair Costs)
Based on fleet maintenance data from over 50,000 trucks, these are the fault codes most likely to strand a Cummins ISX on the side of the road. Learn the root causes and step-by-step diagnostic procedures.
2026-06-26DEF System Fault Codes: A Fleet Manager's Survival Guide to SCR Aftertreatment
DEF and SCR systems are now the leading cause of unscheduled downtime for modern diesel trucks. This guide covers SPN 4364, 3031, 1761, and 4334 — the four codes every fleet manager should know.
2026-06-27DPF Regeneration Problems: Why Your Truck Keeps Asking for a Regen
Frequent DPF regeneration cycles are not normal. They are a symptom of underlying engine problems that, left unaddressed, will destroy the DPF and cost $5,000+ to replace.
2026-06-28J1939 vs J1587: The Complete Comparison (Protocol, Speed, Compatibility)
Why do some fault codes use SPN/FMI (J1939) and others use MID/PID/SID (J1587)? This guide explains the two protocols and why both matter for diagnosing older and newer trucks.
2026-07-25DPF Cleaning Cost Guide 2026: Professional vs DIY ($200-$1,500)
DPF cleaning costs range from $200 for DIY pneumatic cleaning to $1,500 for professional thermal regeneration. This 2026 guide breaks down costs by method, engine brand, and when replacement is the better financial decision.
2026-07-25DEF Pump Replacement Cost: What to Expect ($500-$2,000)
DEF pump replacement costs $500-$2,000 depending on engine brand and labor rates. This guide covers OEM vs aftermarket pricing, labor time, and how to avoid the most common cause of premature DEF pump failure.
2026-07-25Turbocharger Replacement Cost: Complete Price Guide ($1,500-$4,000)
Turbocharger replacement costs $1,500-$4,000 for heavy-duty trucks. This guide covers OEM vs reman pricing by engine brand, labor costs, and how to identify turbo failure before it causes catastrophic engine damage.
2026-07-25EGR Valve Replacement Cost: 2026 Price Guide ($400-$1,500)
EGR valve replacement costs $400-$1,500 for heavy-duty trucks. This 2026 guide covers OEM vs aftermarket pricing by engine brand, labor costs, and when cleaning can save you $800 on replacement.
2026-07-25Cummins ISX vs Detroit DD15: Reliability, Maintenance Cost & Owner-Operator Reviews
Cummins ISX15 vs Detroit DD15: which engine is more reliable and cheaper to maintain? Based on fleet data from 12,000+ trucks, this comparison covers failure rates, maintenance costs, and real owner-operator reviews.
2026-07-25Códigos Comunes del Sistema DEF: Guía Completa
Los códigos del sistema DEF (SPN 3031, 4334, 4364 y 3259) son la causa #1 de tiempo de inactividad en camiones diésel modernos. Esta guía en español explica cada código, sus causas raíz y cómo diagnosticarlos paso a paso.
2026-07-25Problemas SCR en Camiones: Causas y Soluciones
Los problemas SCR en camiones diésel causan el 40% de las averías en carretera. Aprenda las causas más comunes de fallas SCR, cómo diagnosticar el sistema de postratamiento y cuándo reemplazar componentes costosos como el catalizador SCR.
2026-07-25Presión de Aceite Baja: Códigos y Soluciones
La presión de aceite baja (SPN 100) es una falla DETENER MOTOR que puede destruir el motor en minutos. Conozca los códigos SPN 100 FMI 1 y FMI 7, las causas más comunes y los pasos de diagnóstico para evitar daños catastróficos al motor.
2026-07-25Códigos de Falla Cummins X15: Guía PDF 2026 (Descarga Gratis)
El motor Cummins X15 (sucesor del ISX15) es uno de los motores diésel más comunes en Norteamérica. Esta guía en español cubre los códigos de falla más comunes del X15, sus causas y procedimientos de diagnóstico paso a paso.
2026-07-25Cómo Reiniciar el Sistema DEF: 2026 Guía Paso a Paso (Cummins, Detroit, Volvo, PACCAR)
Después de reemplazar componentes del sistema DEF (bomba, dosificador, sensores NOx), debe realizar un reinicio del sistema DEF. Esta guía explica el procedimiento paso a paso para Cummins, Detroit, Volvo y PACCAR.
2026-07-25Check Engine Light On? Complete Diagnostic Flowchart for Diesel Trucks (2026)
When the check engine light illuminates on a heavy-duty diesel truck, the next 60 seconds determine whether you spend $200 or $8,000. This 2026 diagnostic flowchart walks you through the exact decision tree used by master diesel mechanics.
2026-07-25DEF System Reset Procedure: Step-by-Step Guide for All Truck Brands
After replacing any DEF component, the ECM requires a DEF system reset to clear adaptive learning. Skip this procedure and the same fault code returns within 50 miles. This guide covers the exact reset steps for Cummins, Detroit, Volvo, and PACCAR.
2026-07-25SCR System Fault: How to Fix It (Causes, Codes & Step-by-Step Repair)
SCR system faults are the #1 cause of roadside breakdowns on 2010+ diesel trucks. This guide covers the 6 most common SCR fault codes, DIY diagnosis steps, repair cost estimates, and exactly when to call a mechanic vs. attempt the repair yourself.
2026-07-25Low Oil Pressure: Diesel Engine Diagnostic Guide (Causes, Codes & Fix)
Low oil pressure (SPN 100) is a STOP ENGINE fault that can destroy a diesel engine in minutes. This guide covers normal oil pressure ranges, common causes, related fault codes, emergency steps, and repair costs for Cummins, Detroit, Volvo, and PACCAR engines.
2026-07-25Engine Derate Troubleshooting: 5-Step Diagnostic Guide for Diesel Trucks
Engine derate (SPN 1569) is the #1 fault code on heavy-duty diesel trucks. This 5-step diagnostic guide covers derate types (25%, 50%, 5mph), common causes, and exactly how to clear the derate and get back to full power.
2026-07-25Códigos SCR Comunes: Guía de Diagnóstico para Camiones
Los códigos SCR (SPN 4364, 4360, 3361) son responsables del 40% de las averías en carretera de camiones diésel modernos. Esta guía en español explica cada código, sus causas raíz y cómo diagnosticarlos paso a paso sin equipo costoso.
2026-07-25Luz del Motor Encendida: Diagnóstico Paso a Paso
La luz del motor encendida en un camión diésel de servicio pesado puede indicar desde un filtro obstruido hasta una falla inminente del motor. Esta guía en español explica el flujo de diagnóstico paso a paso usado por mecánicos diésel certificados ASE.
2026-07-2510 Códigos de Falla Detroit DD15: Guía Completa 2026 (Causas y Soluciones)
El motor Detroit DD15 es uno de los motores diésel pesados más comunes en Norteamérica. Esta guía en español cubre los códigos de falla más comunes del DD15, sus causas raíz, procedimientos de diagnóstico y costos de reparación basados en datos de flotas.
2026-07-25Presión de Combustible Baja: 6 Códigos Comunes y Soluciones 2026
La presión de combustible baja (SPN 94, SPN 157) es una causa común de pérdida de potencia y paradas en carretera en camiones diésel. Esta guía en español cubre las causas, códigos, diagnóstico y reparación para Cummins, Detroit, Volvo y PACCAR.
2026-07-25Sistema J1939 Explicado: Protocolo, Códigos y Diagnóstico
El protocolo SAE J1939 es el estándar para diagnóstico de camiones diésel modernos. Esta guía en español explica cómo funciona J1939, la diferencia entre SPN/FMI y MID/PID/SID, y cómo usar códigos J1939 para diagnóstico preciso.
2026-07-2812 Códigos de Falla Motor Cummins X15: Guía Completa 2026 con PDF
Guía completa 2026 de códigos de falla del motor Cummins X15: SPN 94, SPN 111, SPN 1569, SPN 5246 y más. Causas, diagnóstico paso a paso y costos de reparación para flotas y mecánicos diésel.
2026-07-28Sistema DEF en Camiones: Todo lo que Necesita Saber (2026)
Guía completa 2026 del sistema DEF en camiones diésel: cómo funciona, códigos SPN 3031, 4334, 4364, 3259, costos de reparación y procedimientos de diagnóstico paso a paso para mecánicos y flotas.
2026-07-2810 Códigos de Falla Detroit DD15 Más Comunes 2026: Causas y Soluciones
Los 10 códigos de falla más comunes del motor Detroit DD15: SPN 1761, 100, 110, 4364, 5246 y más. Causas, diagnóstico y costos de reparación basados en datos de flotas comerciales.
2026-07-28Presión de Aceite Baja: Diagnóstico Completo
Guía completa de diagnóstico para presión de aceite baja en motores diésel: SPN 100, causas, procedimientos de prueba con manómetro mecánico, costos de reparación y cuándo detener el motor.
2026-07-28Luz del Motor: Diagnóstico Paso a Paso
Guía paso a paso para diagnosticar la luz del motor (check engine light) en camiones diésel: códigos SPN comunes, matriz de síntomas, regla de las 50 millas y cuándo detener el motor.
2026-07-28DEF System Complete Guide: Diagnosis, Codes & Repair Costs (2026)
Complete 2026 guide to the Diesel Exhaust Fluid (DEF) system on heavy-duty trucks: how SCR works, SPN 3031/4334/4364/3259 codes, diagnosis, repair costs, and prevention strategies for fleets.
2026-07-28Cummins X15 Common Fault Codes: Complete Guide
Complete guide to Cummins X15 common fault codes: SPN 1569, 102, 94, 4364, 5246 and more. Root causes, diagnostic procedures, repair costs, and prevention strategies for fleet managers.
2026-07-28SCR System Fault: Complete Troubleshooting Guide
Complete troubleshooting guide for SCR system faults on heavy-duty diesel trucks: SPN 4364, 3482, 4334, root causes, diagnostic procedures, repair costs, and prevention strategies.
2026-07-30Diesel Particulate Filter (DPF) Regeneration: Complete Guide
Complete guide to DPF regeneration on heavy-duty diesel trucks. Covers passive, active, and parked regeneration, soot/ash accumulation, SPN 3251 and 5484 fault diagnostics, and prevention strategies.
2026-08-01DEF Quality Testing Field Guide: 5-Minute Refractometer Protocol
Contaminated DEF causes 70% of SCR system failures. This guide covers the 5-minute refractometer test protocol, API certification verification, and field indicators of degraded DEF that every fleet technician should know.
2026-08-01SCR Inducement Failure: Complete 2026 Guide (4 Stages, 6 Causes, Step-by-Step Fix)
SCR inducement locks engine speed to 5 MPH when the aftertreatment system fails. This guide covers the 4-stage inducement sequence, EPA-mandated timeframes, and the 6 most common root causes with diagnostic procedures.
Diagnose by Symptom
How We Build This Database
Every fault code on DTC Hub goes through a rigorous four-step verification process before publication. We combine public SAE standards with OEM service documentation to create the most accurate, roadside-ready diagnostic reference available for free.
Fault code definitions extracted from SAE J1939 Digital Annex and J1587/J1708 standards — the same source data used by OEM engineering teams.
Each code is cross-referenced against manufacturer-specific service documentation from Cummins, Detroit Diesel, Volvo, PACCAR, and International.
Technical SAE terminology is translated into actionable, plain English suitable for roadside use by drivers and mechanics without engineering backgrounds.
Every code page is reviewed by a fleet data analyst for technical accuracy, clarity, and safety. STOP ENGINE codes receive priority review.