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 HDS or the scan tool during acceleration using wide open throttle.

Is there 0.5 V or less?


YES - Go to 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/ 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 HDS or the scan tool.

Is there 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 ECM/PCM connector A (31P).

11.Check for continuity between the 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 - 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