P0131

DTC P0131: Primary HO2S (Sensor 1) Circuit Low Voltage (2004-2005 models)

NOTE: Before you troubleshoot, record all freeze data and review the general troubleshooting information.

1. Reset the ECM.
2. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on.
3. Check the primary HO2S (Sensor 1) output voltage with a scan tool or the HDS during acceleration using wide open throttle.

Does the voltage stay at 0.1 V or less?

YES - Go to step 4.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the primary HO2S (Sensor 1) and at the ECM.

4. Turn the ignition switch OFF.
5. Disconnect the primary HO2S (Sensor 1) 4P connector.
6. Turn the ignition switch ON (II).
7. Check the primary HO2S (Sensor 1) output voltage with a scan tool or the HDS.

Is there 0.1 V or less?

YES - Go to step 8.

NO - Replace the primary HO2S (Sensor 1).

8. Turn the ignition switch OFF.
9. Disconnect ECM connector C (31P).




10. Check for continuity between primary HO2S (Sensor 1) 4P connector terminal No. 1 and body ground.

Is there continuity?

YES - Repair short in the wire between the ECM (C16) and the primary HO2S (Sensor 1).

NO - Substitute a known-good ECM and recheck. If the symptom/indication goes away, replace the original ECM.