OBD-II Fault Code Library
Got a Check Engine Light? Plug in a scanner, get the code, and look it up here. We provide the generic meaning, common causes, and cross-reference the code against known faults in specific cars.
Coolant Thermostat (Coolant Temp Below Regulating Temp)
The engine is not reaching its optimal operating temperature within the expected timeframe, usually because the thermostat is stuck open.
System Too Lean (Bank 1)
The engine is running 'lean' on Bank 1, meaning there is too much air and not enough fuel in the combustion mixture.
Turbo/Supercharger Overboost Condition
The manifold absolute pressure (MAP) sensor is detecting boost pressure from the turbocharger that exceeds the safe maximum limit set by the ECM.
Random/Multiple Cylinder Misfire Detected
The Engine Control Module (ECM) has detected a misfire occurring randomly or across multiple cylinders. A misfire means the air/fuel mixture in the cylinder is not burning properly.
Glow Plug/Heater Circuit 'A' Malfunction
The ECM has detected a malfunction in the glow plug heating circuit, which is required to help ignite diesel fuel when the engine is cold.
Exhaust Gas Recirculation (EGR) Flow Insufficient
The ECM is detecting that not enough exhaust gas is being recirculated back into the intake manifold by the EGR system.
Catalyst System Efficiency Below Threshold (Bank 1)
The downstream oxygen sensor is detecting that the catalytic converter on Bank 1 is not operating at maximum efficiency to reduce emissions.
Generator Control Circuit Malfunction
The Engine Control Module (ECM) has detected a fault in the alternator's control circuit, meaning the battery may not be charging correctly.
Transmission Control System Malfunction
This is an informational code indicating that the Transmission Control Module (TCM) has detected a fault and has requested the ECM to turn on the Check Engine Light.
Diesel Particulate Filter (DPF) Efficiency Below Threshold
The pressure sensors across the DPF indicate that the filter is clogged with soot and ash, and is no longer able to regenerate efficiently.