DTC codes
Look up an OBD-II fault code: what it means on every car or on your make, and how to track it down.
How to read a code
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 4
- AreaAuxiliary emission controls
- 20
- FaultThe specific fault in that area
Read the code
Note every stored and pending code your scanner shows, such as P0420.
Find it
Search by code or by words. For a manufacturer code (P1, B1, C1, U1) pick your make: its meaning differs by make.
Open the code
Its page explains the symptoms, likely causes, the checks to run and the fixes.
- P21B2Generic · PowertrainExcessive Time To Enter Closed Loop NOx Adsorber Control
- P21B3Generic · PowertrainClosed Loop NOx Adsorber Control At Limit - Too High
- P21B4Generic · PowertrainNOx Adsorber - Over Temperature Bank 1
- P21B5Generic · PowertrainNOx Adsorber - Over Temperature Bank 2
- P21B6Generic · PowertrainCold Start Cylinder 1 Injection Timing
- P21B7Generic · PowertrainCold Start Cylinder 2 Injection Timing
- P21B8Generic · PowertrainCold Start Cylinder 3 Injection Timing
- P21B9Generic · PowertrainCold Start Cylinder 4 Injection Timing
- P21BAGeneric · PowertrainCold Start Cylinder 5 Injection Timing
- P21BBGeneric · PowertrainCold Start Cylinder 6 Injection Timing
- P21BCGeneric · PowertrainCold Start Cylinder 7 Injection Timing
- P21BDGeneric · PowertrainCold Start Cylinder 8 Injection Timing
- P21BEGeneric · PowertrainCold Start Cylinder 9 Injection Timing
- P21BFGeneric · PowertrainCold Start Cylinder 10 Injection Timing
- P21C0Generic · PowertrainCold Start Cylinder 11 Injection Timing
- P21C1Generic · PowertrainCold Start Cylinder 12 Injection Timing
- P21C2Generic · PowertrainReductant Heater Relay Control Circuit/Open
- P21C3Generic · PowertrainReductant Heater Relay Control Circuit Low
- P21C4Generic · PowertrainReductant Heater Relay Control Circuit High
- P21C5Generic · PowertrainReductant Level Sensor A Stuck
- P21C6Generic · PowertrainReductant Level Sensor B Stuck
- P21C7Generic · PowertrainReductant Control Module Power Relay/Relays Control Circuit/Open
- P21C8Generic · PowertrainReductant Control Module Power Relay/Relays Control Circuit Low
- P21C9Generic · PowertrainReductant Control Module Power Relay/Relays Control Circuit High
- P21CAGeneric · PowertrainReductant Control Module Supply Voltage Circuit
- P21CBGeneric · PowertrainReductant Control Module Supply Voltage Low
- P21CCGeneric · PowertrainReductant Control Module Supply Voltage High
- P21CDGeneric · PowertrainReductant Quality Module Supply Voltage Low
- P21CEGeneric · PowertrainReductant Quality Module Performance
- P21CFGeneric · PowertrainCylinder 1 Injector B Circuit/Open