Related System Faults

Many of the OBD II system diagnostics will not run if the Powertrain Control Module (PCM)/Engine Control Module (ECM) detects a fault on a related system or component. One example would be that if the PCM/ECM detected a Misfire fault, the diagnostics on the catalytic converter would be suspended until the Misfire fault was repaired. If the Misfire fault is severe enough, the catalytic converter can be damaged due to overheating and will never set a Catalyst DTC until the Misfire fault is repaired and the Catalyst diagnostic is allowed to run to completion. If this happens, the customer may have to make two trips to the dealership in order to repair the vehicle.