Circuit/System Testing

IMPORTANT:

All modules must be powered down or misdiagnosis may result.
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
For DTC P0131 and P0132, in order to ensure that the performance of the catalyst has not been affected by the fault that set this DTC, operate the vehicle within the Conditions for Running and Setting DTC P0420 and verify that P0420 runs and passes. Refer to DTC P0420 .

Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
Ignition OFF, disconnect the harness connector at the appropriate HO2S.
Ignition OFF, measure for less than 5 ohms resistance between the appropriate HO2S low signal circuit terminal A and ground.
- If more than the specified range, test the appropriate HO2S low signal circuit for an open/high resistance. If the circuit tests normal, replace the engine control module (ECM).
Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
- If more than the specified value, test the appropriate HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- If less than the specified value, test the appropriate HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
Ignition ON, install a 3A fused jumper wire at the HO2S high signal circuit terminal B. Toggle the jumper wire between the HO2S low signal circuit terminal A and the battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.
- If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
If all circuits test normal, replace the appropriate HO2S.