DTC Troubleshooting

DTC P0138: Secondary HO2S (Sensor 2) Circuit High Voltage

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.

1. Turn the ignition switch ON (II).
2. Clear the DTC with the HDS.
3. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on, then let it idle.
4. Check the HO2S S2 in the DATA LIST with the HDS.

Does the voltage stay at 1.25 V or more?

YES - Go to step 5.

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

5. Turn the ignition switch OFF.
6. Disconnect the secondary HO2S (Sensor 2) 4P connector.




7. Connect secondary HO2S (Sensor 2) 4P connector terminals No. 1 and No. 2 with a jumper wire.
8. Turn the ignition switch ON (II).
9. Check the HO2S S2 in the DATA LIST with the HDS.

Does the voltage stay at 1.25 V or more?

YES - Go to step 10.

NO - Go to step 19.

10. Turn the ignition switch OFF.
11. Remove the jumper wire from the secondary HO2S (Sensor 2) 4P connector.




12. Connect secondary HO2S (Sensor 2) 4P connector terminal No. 1 to body ground with a jumper wire.
13. Turn the ignition switch ON (II).
14. Check the HO2S S2 in the DATA LIST with the HDS.

Does the voltage stay at 1.25 V or more?

YES - Go to step 15.

NO - Repair open in the wire between the PCM (B33) and the secondary HO2S (Sensor 2), then go to step 21.

15. Turn the ignition switch OFF.
16. Jump the SCS line with the HDS.
17. Disconnect PCM connector C (44P).




18. Check for continuity between PCM connector terminal C27 and body ground.

Is there continuity?

YES - Go to step 29.

NO - Repair open in the wire between the PCM (C27) and the secondary HO2S (Sensor 2), then go to step 21.

19. Turn the ignition switch OFF.
20. Replace the secondary HO2S (Sensor 2).
21. Reconnect all connectors.
22. Turn the ignition switch ON (II).
23. Reset the PCM with the HDS.
24. Do the PCM idle learn procedure.
25. Start the engine, and let it idle without load (in Park or neutral) until the radiator fan comes on.
26. Test-drive under these conditions:
- ECT SENSOR 1 above 158 °F (70 °C)
- Transmission in D position
- Engine speed between 1,500 - 3,000 rpm
- Maintain a steady speed about 1 minute or more

27. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0138 indicated?

YES - Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the PCM, then go to step 1.

NO - Go to step 28.

28. Monitor the OBD STATUS for DTC P0138 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?

YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 27, go to the indicated DTCs troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the PCM, then go to step 1. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to step 25.

29. Reconnect all connectors.
30. Update the PCM if it does not have the latest software, or substitute a known-good PCM.
31. Start the engine, and let it idle without load (in Park or neutral) until the radiator fan comes on, then let it idle.
32. Test-drive under these conditions:
- ECT SENSOR 1 above 158 °F (70 °C)
- Transmission in D position
- Engine speed between 1,500 - 3,000 rpm
- Maintain a steady speed about 1 minute or more

33. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0138 indicated?

YES - Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the PCM. If the PCM was updated, substitute a known-good PCM, then go to step 31. If the PCM was substituted, go to step 1.

NO - Go to step 34.

34. Monitor the OBD STATUS for DTC P0138 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?

YES - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM. If any other Temporary DTCs or DTCs were indicated in step 33, go to the indicated DTCs troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the PCM. If the PCM was updated, substitute a known-good PCM, then go to step 31. If the PCM was substituted, go to step 1. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to step 31.