DTC Troubleshooting: P0138 (63-2)

DTC P0138 (63-2):  Secondary HO2S(Sensor 2) Circuit High 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 secondary HO2S (Sensor 2) output voltage at 3,000 rpm (min-1) with the scan tool.

Does the voltage stay at 1.0 V or more?


YES - Go to 4.


NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the  secondary HO2S (Sensor 2) and the at  ECM/ PCM.n


4.Turn the ignition switch OFF.

5.Disconnect the secondary HO2S (Sensor 2) 6P connector.

6.Connect secondary HO2S (Sensor 2) 6P connector terminals No. 1 and No. 2 with a jumper wire.

 

7.Turn the ignition switch ON (II).

8.Check the secondary HO2S (Sensor 2) output voltage with the scan tool.

Is there 1.0 V or more?


YES - Go to 9.


NO - Replace the  secondary HO2S (Sensor 2).n


9.Turn the ignition switch OFF.

10.Connect ECM/PCM connector terminals E2 and E4 with a jumper wire.

 

11.Turn the ignition switch ON (II).

12.Check the secondary HO2S (Sensor 2) output voltage with the scan tool.

Is there 1.0 V or more?


YES - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original  ECM/ PCM.n


NO - Repair open in the wire between the  ECM/ PCM (E2, E4) and the  secondary HO2S (Sensor 2).n