DTC Troubleshooting: P0131 (1-1)

DTC P0131 (1-1):  Primary HO2S(Sensor 1) 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 primary HO2S (Sensor 1) 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  primary HO2S (Sensor 1) 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 primary HO2S (Sensor 1) 4P connector.

7.Turn the ignition switch ON (II).

8.Check the primary HO2S (Sensor 1) output voltage with the scan tool.

Does it stay at 0.5 V or less?


YES - Go to 9.


NO - Replace the  primary HO2S (Sensor 1).n

9.Turn the ignition switch OFF.

10.Disconnect the negative cable from the battery.

11.Disconnect ECM/PCM connector A (31P).

12.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/ PCM (A6) and the  primary HO2S (Sensor 1).n


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