Diagnostic Trouble Codes (DTCs)

With OBD II, different DTC faults have different priorities according to regulations. As a result, the priorities determine MIL illumination and DTC erasure. DTCs are entered according to individual priority. DTCs with a higher priority overwrite lower priority DTCs.

Priorities
- Priority 0 - Non-emissions related trouble codes
- Priority 1 - One trip failure of a two trip fault for non-fuel system and non-misfire.
- Priority 2 - One trip failure of a two trip fault for fuel system (rich/lean) or misfire.
- Priority 3 - Two trip failure for a non-fuel system and non-misfire or matured one trip comprehensive component fault.
- Priority 4 - Two trip failure or matured fault for fuel system (rich/lean) and misfire or one trip catalyst damaging misfire.

Non-emissions related failures have no priority. One trip failures of two trip faults have low priority. Two trip failures or matured faults have higher priority. One and two trip failures of fuel system and misfire monitor take precedence over non-fuel system and non-misfire failures.