Diagnostic Trouble Codes (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.