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GM Duramax Fault Codes — Complete Guide

GM Duramax SPN/FMI codes cover L5P 6.6L, LML 6.6L, LBZ 6.6L. This hub lists 202 diagnostic pages with symptoms, ranked causes, scan-tool steps, and 2026 repair costs — use INSITE, DiagnosticLink, or EST depending on your engine family.

By Professional Diesel Repair TeamPublished: January 2026Last updated: September 2026

How We Tested and Verified

GM Duramax fault code definitions cross-checked against SAE J1939-71 and GM Duramax OEM service bulletins. Diagnostic tips validated by field technicians September 2026.

GM Duramax Engine Platforms

GM Duramax engines covered on this site include: L5P 6.6L, LML 6.6L, LBZ 6.6L. Diagnostic procedures vary by platform — always verify against your specific engine serial number and calibration.

Most Common GM Duramax Fault Codes

CodeComponentSeverityDefinition
SPN P0217 FMI N/AEngine Coolant Over Temperature ConditionCriticalEngine Coolant Over Temperature Condition
SPN P0217 FMI N/AEngine Coolant Over Temperature ConditionCriticalEngine Coolant Over Temperature Condition
SPN P0217 FMI N/AEngine Coolant Over Temperature ConditionCriticalEngine Coolant Over Temperature Condition
SPN P0217 FMI N/AEngine Coolant Over Temperature ConditionCriticalEngine Coolant Over Temperature Condition
SPN P0217 FMI N/AEngine Coolant Over Temperature ConditionCriticalEngine Coolant Over Temperature Condition
SPN P0217 FMI N/AEngine Coolant Over Temperature ConditionCriticalEngine Coolant Over Temperature Condition
SPN P0217 FMI N/AEngine Coolant Over Temperature ConditionCriticalEngine Coolant Over Temperature Condition
SPN P0524 FMI N/AEngine Oil PressureCriticalEngine Oil Pressure Too Low
SPN 0093 FMI N/AFuel SystemHighFuel System Large Leak Detected
SPN 2146 FMI N/AFuel Injector Group AHighFuel Injector Group A Supply Voltage Circuit/Open
SPN 2569 FMI N/ATurbo Boost Control Position SensorHighTurbo Boost Control Position Sensor Circuit Low
SPN P003A FMI N/ATurbocharger Boost Control Position Exceeded Learning LimitHighTurbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
SPN P003A FMI N/ATurbocharger Boost Control Position Exceeded Learning LimitHighTurbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
SPN P003A FMI N/ATurbocharger Boost Control Position Exceeded Learning LimitHighTurbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
SPN P003A FMI N/ATurbocharger Boost Control Position Exceeded Learning LimitHighTurbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
SPN P003A FMI N/ATurbocharger Boost Control Position Exceeded Learning LimitHighTurbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
SPN P003A FMI N/ATurbocharger Boost Control Position Exceeded Learning LimitHighTurbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
SPN P003A FMI N/ATurbocharger Boost Control Position Exceeded Learning LimitHighTurbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
SPN P0046 FMI N/ATurbocharger Boost Control Circuit Range/PerformanceHighTurbocharger/Supercharger Boost Control 'A' Circuit Range/Performance
SPN P0046 FMI N/ATurbocharger Boost Control Circuit Range/PerformanceHighTurbocharger/Supercharger Boost Control 'A' Circuit Range/Performance

GM Duramax-Specific Diagnostic Tips

  • GM GDS2 or Tech 2 required for L5P fuel rail pressure bi-directional tests.
  • LML CP4.2 pump failure rate is high — install disaster prevention kit or lift pump.
  • L5P NOx sensor failures often follow DEF injector crystallization — clean before sensor swap.

All GM Duramax Fault Codes (202)

SPN 0093 FMI N/A

Fuel System

SPN 0094 FMI N/A

Fuel System

SPN 0130 FMI N/A

O2 Sensor Bank 1 Sensor 1

SPN 0243 FMI N/A

Turbocharger Wastegate Solenoid A

SPN 0405 FMI N/A

EGR Position Sensor

SPN 0470 FMI N/A

Exhaust Pressure Sensor

SPN 2031 FMI N/A

Exhaust Gas Temperature Sensor

SPN 2032 FMI N/A

Exhaust Gas Temperature Sensor

SPN 2146 FMI N/A

Fuel Injector Group A

SPN 2569 FMI N/A

Turbo Boost Control Position Sensor

SPN P003A FMI N/A

Turbocharger Boost Control Position Exceeded Learning Limit

SPN P003A FMI N/A

Turbocharger Boost Control Position Exceeded Learning Limit

SPN P003A FMI N/A

Turbocharger Boost Control Position Exceeded Learning Limit

SPN P003A FMI N/A

Turbocharger Boost Control Position Exceeded Learning Limit

SPN P003A FMI N/A

Turbocharger Boost Control Position Exceeded Learning Limit

SPN P003A FMI N/A

Turbocharger Boost Control Position Exceeded Learning Limit

SPN P003A FMI N/A

Turbocharger Boost Control Position Exceeded Learning Limit

SPN P0046 FMI N/A

Turbocharger Boost Control Circuit Range/Performance

SPN P0046 FMI N/A

Turbocharger Boost Control Circuit Range/Performance

SPN P0046 FMI N/A

Turbocharger Boost Control Circuit Range/Performance

SPN P0046 FMI N/A

Turbocharger Boost Control Circuit Range/Performance

SPN P0046 FMI N/A

Turbocharger Boost Control Circuit Range/Performance

SPN P0046 FMI N/A

Turbocharger Boost Control Circuit Range/Performance

SPN P0046 FMI N/A

Turbocharger Boost Control Circuit Range/Performance

SPN P0087 FMI N/A

Fuel Rail Pressure Too Low

SPN P0087 FMI N/A

Fuel Rail Pressure Too Low

SPN P0087 FMI N/A

Fuel Rail Pressure Too Low

SPN P0087 FMI N/A

Fuel Rail Pressure Too Low

SPN P0087 FMI N/A

Fuel Rail Pressure Too Low

SPN P0087 FMI N/A

Fuel Rail Pressure Too Low

SPN P0087 FMI N/A

Fuel Rail Pressure Too Low

SPN P0088 FMI N/A

Fuel Rail Pressure Sensor

SPN P0088 FMI N/A

Fuel Rail Pressure Sensor

SPN P0088 FMI N/A

Fuel Rail Pressure Sensor

SPN P0088 FMI N/A

Fuel Rail Pressure Sensor

SPN P0088 FMI N/A

Fuel Rail Pressure Sensor

SPN P0088 FMI N/A

Fuel Rail Pressure Sensor

SPN P0088 FMI N/A

Fuel Rail Pressure Sensor

SPN P0101 FMI N/A

MAF Sensor Range/Performance

SPN P0101 FMI N/A

MAF Sensor Range/Performance

SPN P0101 FMI N/A

MAF Sensor Range/Performance

SPN P0101 FMI N/A

MAF Sensor Range/Performance

SPN P0101 FMI N/A

MAF Sensor Range/Performance

SPN P0101 FMI N/A

MAF Sensor Range/Performance

SPN P0101 FMI N/A

MAF Sensor Range/Performance

SPN P0116 FMI N/A

Engine Coolant Temperature Sensor

SPN P0117 FMI N/A

Engine Coolant Temperature Circuit

SPN P0182 FMI N/A

Fuel Temperature Sensor Circuit

SPN P0193 FMI N/A

Fuel Rail Pressure Sensor Circuit High

SPN P0193 FMI N/A

Fuel Rail Pressure Sensor Circuit High

SPN P0193 FMI N/A

Fuel Rail Pressure Sensor Circuit High

SPN P0193 FMI N/A

Fuel Rail Pressure Sensor Circuit High

SPN P0193 FMI N/A

Fuel Rail Pressure Sensor Circuit High

SPN P0193 FMI N/A

Fuel Rail Pressure Sensor Circuit High

SPN P0193 FMI N/A

Fuel Rail Pressure Sensor Circuit High

SPN P0201 FMI N/A

Fuel Injector Cylinder 1

SPN P0202 FMI N/A

Fuel Injector Circuit - Cylinder 2

SPN P0203 FMI N/A

Fuel Injector 3 Control Circuit

SPN P0217 FMI N/A

Engine Coolant Over Temperature Condition

SPN P0217 FMI N/A

Engine Coolant Over Temperature Condition

SPN P0217 FMI N/A

Engine Coolant Over Temperature Condition

SPN P0217 FMI N/A

Engine Coolant Over Temperature Condition

SPN P0217 FMI N/A

Engine Coolant Over Temperature Condition

SPN P0217 FMI N/A

Engine Coolant Over Temperature Condition

SPN P0217 FMI N/A

Engine Coolant Over Temperature Condition

SPN P0219 FMI N/A

Engine Speed Control

SPN P0234 FMI N/A

Turbocharger Boost Control

SPN P0234 FMI N/A

Turbocharger Boost Control

SPN P0234 FMI N/A

Turbocharger Boost Control

SPN P0234 FMI N/A

Turbocharger Boost Control

SPN P0234 FMI N/A

Turbocharger Boost Control

SPN P0234 FMI N/A

Turbocharger Boost Control

SPN P0234 FMI N/A

Turbocharger Boost Control

SPN P0299 FMI N/A

Turbocharger Underboost

SPN P0299 FMI N/A

Turbocharger Underboost

SPN P0299 FMI N/A

Turbocharger Underboost

SPN P0299 FMI N/A

Turbocharger Underboost

SPN P0299 FMI N/A

Turbocharger Underboost

SPN P0299 FMI N/A

Turbocharger Underboost

SPN P0299 FMI N/A

Turbocharger Underboost

SPN P0335 FMI N/A

Crankshaft Position Sensor Circuit

SPN P0340 FMI N/A

Camshaft Position Sensor

SPN P0341 FMI N/A

Camshaft Position Sensor

SPN P0401 FMI N/A

EGR Flow Insufficient

SPN P0401 FMI N/A

EGR Flow Insufficient

SPN P0401 FMI N/A

EGR Flow Insufficient

SPN P0401 FMI N/A

EGR Flow Insufficient

SPN P0401 FMI N/A

EGR Flow Insufficient

SPN P0401 FMI N/A

EGR Flow Insufficient

SPN P0401 FMI N/A

EGR Flow Insufficient

SPN P0402 FMI N/A

EGR System

SPN P0402 FMI N/A

EGR System

SPN P0402 FMI N/A

EGR System

SPN P0402 FMI N/A

EGR System

SPN P0402 FMI N/A

EGR System

SPN P0402 FMI N/A

EGR System

SPN P0402 FMI N/A

EGR System

SPN P0403 FMI N/A

EGR Control Circuit

SPN P0404 FMI N/A

EGR Circuit Range/Performance

SPN P0471 FMI N/A

Exhaust Pressure Sensor

SPN P0472 FMI N/A

Exhaust Backpressure Sensor Circuit

SPN P0500 FMI N/A

Vehicle Speed Sensor

SPN P0523 FMI N/A

Engine Oil Pressure Sensor Circuit High

SPN P0523 FMI N/A

Engine Oil Pressure Sensor Circuit High

SPN P0523 FMI N/A

Engine Oil Pressure Sensor Circuit High

SPN P0523 FMI N/A

Engine Oil Pressure Sensor Circuit High

SPN P0523 FMI N/A

Engine Oil Pressure Sensor Circuit High

SPN P0523 FMI N/A

Engine Oil Pressure Sensor Circuit High

SPN P0523 FMI N/A

Engine Oil Pressure Sensor Circuit High

SPN P0524 FMI N/A

Engine Oil Pressure

SPN P0526 FMI N/A

Fan Speed Sensor Circuit

SPN P0546 FMI N/A

Exhaust Gas Temperature Sensor 1 Circuit

SPN P0546 FMI N/A

Exhaust Gas Temperature Sensor 1 Circuit

SPN P0546 FMI N/A

Exhaust Gas Temperature Sensor 1 Circuit

SPN P0546 FMI N/A

Exhaust Gas Temperature Sensor 1 Circuit

SPN P0546 FMI N/A

Exhaust Gas Temperature Sensor 1 Circuit

SPN P0546 FMI N/A

Exhaust Gas Temperature Sensor 1 Circuit

SPN P0546 FMI N/A

Exhaust Gas Temperature Sensor 1 Circuit

SPN P0562 FMI N/A

Charging System / Battery

SPN P0611 FMI N/A

Fuel Injector Control Module

SPN P0638 FMI N/A

Intake Throttle Valve Control

SPN P0670 FMI N/A

Glow Plug Control Circuit

SPN P0670 FMI N/A

Glow Plug Control Circuit

SPN P0670 FMI N/A

Glow Plug Control Circuit

SPN P0670 FMI N/A

Glow Plug Control Circuit

SPN P0670 FMI N/A

Glow Plug Control Circuit

SPN P0670 FMI N/A

Glow Plug Control Circuit

SPN P0670 FMI N/A

Glow Plug Control Circuit

SPN P1093 FMI N/A

Fuel Rail Pressure Too Low During Load

SPN P1093 FMI N/A

Fuel Rail Pressure Too Low During Load

SPN P1093 FMI N/A

Fuel Rail Pressure Too Low During Load

SPN P1093 FMI N/A

Fuel Rail Pressure Too Low During Load

SPN P1093 FMI N/A

Fuel Rail Pressure Too Low During Load

SPN P1093 FMI N/A

Fuel Rail Pressure Too Low During Load

SPN P1093 FMI N/A

Fuel Rail Pressure Too Low During Load

SPN P2002 FMI N/A

Diesel Particulate Filter

SPN P2002 FMI N/A

Diesel Particulate Filter

SPN P2002 FMI N/A

Diesel Particulate Filter

SPN P2002 FMI N/A

Diesel Particulate Filter

SPN P2002 FMI N/A

Diesel Particulate Filter

SPN P2002 FMI N/A

Diesel Particulate Filter

SPN P2002 FMI N/A

Diesel Particulate Filter

SPN P2033 FMI N/A

Exhaust Gas Temperature Sensor Bank 1 Sensor 2

SPN P203F FMI N/A

Reductant System Performance

SPN P203F FMI N/A

Reductant System Performance

SPN P203F FMI N/A

Reductant System Performance

SPN P203F FMI N/A

Reductant System Performance

SPN P203F FMI N/A

Reductant System Performance

SPN P203F FMI N/A

Reductant System Performance

SPN P203F FMI N/A

Reductant System Performance

SPN P20B9 FMI N/A

Reductant Temperature

SPN P20BA FMI N/A

DEF Tank Heater

SPN P20EE FMI N/A

SCR NOx Catalyst

SPN P20EE FMI N/A

SCR NOx Catalyst

SPN P20EE FMI N/A

SCR NOx Catalyst

SPN P20EE FMI N/A

SCR NOx Catalyst

SPN P20EE FMI N/A

SCR NOx Catalyst

SPN P20EE FMI N/A

SCR NOx Catalyst

SPN P20EE FMI N/A

SCR NOx Catalyst

SPN P2149 FMI N/A

Fuel Injector Group B Supply Voltage Circuit

SPN P2149 FMI N/A

Fuel Injector Group B Supply Voltage Circuit

SPN P2149 FMI N/A

Fuel Injector Group B Supply Voltage Circuit

SPN P2149 FMI N/A

Fuel Injector Group B Supply Voltage Circuit

SPN P2149 FMI N/A

Fuel Injector Group B Supply Voltage Circuit

SPN P2149 FMI N/A

Fuel Injector Group B Supply Voltage Circuit

SPN P2149 FMI N/A

Fuel Injector Group B Supply Voltage Circuit

SPN P244B FMI N/A

DPF Differential Pressure

SPN P2452 FMI N/A

DPF Pressure Sensor Circuit

SPN P2452 FMI N/A

DPF Pressure Sensor Circuit

SPN P2452 FMI N/A

DPF Pressure Sensor Circuit

SPN P2452 FMI N/A

DPF Pressure Sensor Circuit

SPN P2452 FMI N/A

DPF Pressure Sensor Circuit

SPN P2452 FMI N/A

DPF Pressure Sensor Circuit

SPN P2452 FMI N/A

DPF Pressure Sensor Circuit

SPN P2459 FMI N/A

DPF Regeneration Frequency

SPN P2459 FMI N/A

DPF Regeneration Frequency

SPN P2459 FMI N/A

DPF Regeneration Frequency

SPN P2459 FMI N/A

DPF Regeneration Frequency

SPN P2459 FMI N/A

DPF Regeneration Frequency

SPN P2459 FMI N/A

DPF Regeneration Frequency

SPN P2459 FMI N/A

DPF Regeneration Frequency

SPN P2463 FMI N/A

DPF Restriction - Soot Accumulation

SPN P2463 FMI N/A

DPF Restriction - Soot Accumulation

SPN P2463 FMI N/A

DPF Restriction - Soot Accumulation

SPN P2463 FMI N/A

DPF Restriction - Soot Accumulation

SPN P2463 FMI N/A

DPF Restriction - Soot Accumulation

SPN P2463 FMI N/A

DPF Restriction - Soot Accumulation

SPN P2463 FMI N/A

DPF Restriction - Soot Accumulation

SPN P24A4 FMI N/A

DPF Restriction - Forced Regeneration Limit Reached

SPN P24A4 FMI N/A

DPF Restriction - Forced Regeneration Limit Reached

SPN P24A4 FMI N/A

DPF Restriction - Forced Regeneration Limit Reached

SPN P24A4 FMI N/A

DPF Restriction - Forced Regeneration Limit Reached

SPN P24A4 FMI N/A

DPF Restriction - Forced Regeneration Limit Reached

SPN P24A4 FMI N/A

DPF Restriction - Forced Regeneration Limit Reached

SPN P24A4 FMI N/A

DPF Restriction - Forced Regeneration Limit Reached

SPN P2563 FMI N/A

Turbocharger Boost Control Position Sensor Circuit

SPN P2563 FMI N/A

Turbocharger Boost Control Position Sensor Circuit

SPN P2563 FMI N/A

Turbocharger Boost Control Position Sensor Circuit

SPN P2563 FMI N/A

Turbocharger Boost Control Position Sensor Circuit

SPN P2563 FMI N/A

Turbocharger Boost Control Position Sensor Circuit

SPN P2563 FMI N/A

Turbocharger Boost Control Position Sensor Circuit

SPN P2563 FMI N/A

Turbocharger Boost Control Position Sensor Circuit

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