## DTC Troubleshooting: P0131 (1-1)

DTC P0131 (1-1): | HO2S Circuit Low Voltage

1. | Reset the ECM/PCM.

2. | Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on.

3. | Check the HO2S output voltage with the scan tool during acceleration using wide open throttle. Does the voltage stay at 0.5 V or less? YES - Go to 4. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the HO2S and at the ECM/ PCM.n

4. | Check the fuel pressure. Is it normal? YES - Go to 5. NO - Repair the fuel supply system.n

5. | Turn the ignition switch OFF.

6. | Disconnect the HO2S 4P connector.

7. | Turn the ignition switch ON (II).

8. | Check the HO2S output voltage with the scan tool. Does it stay at 0.5 V or less? YES - Go to 9. NO - Replace the HO2S.n

9. | Turn the ignition switch OFF.

10. | Disconnect ECM/PCM connector A (31P).

11. | Check for continuity between the HO2S 4P connector terminal No. 1 and body ground. Is there continuity? YES - Repair short in the wire between the ECM/PCM (A6) and the HO2S.n NO - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.n