P0138

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 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 ECM.

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




8. Connect secondary HO2S (Sensor 2) 4P connector terminals No. 1 and No. 2 with a jumper wire.
9. Turn the ignition switch ON (II).
10. 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 11.

NO - Go to step 20.

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




13. Connect secondary HO2S (Sensor 2) 4P connector terminal No. 2 to body ground with a jumper wire.
14. Turn the ignition switch ON (II).
15. 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 16.

NO - Repair open in the wire between the ECM (B33) and the secondary HO2S (Sensor 2), then go to step 22.

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




19. Check for continuity between ECM connector terminal C27 and body ground.

Is there continuity?

YES - Go to step 30.

NO - Repair open in the wire between the ECM (C27) and the secondary HO2S (Sensor 2), then go to step 22.

20. Turn the ignition switch OFF.
21. Replace the secondary HO2S (Sensor 2).
22. Reconnect all connectors.
23. Turn the ignition switch ON (II).
24. Reset the ECM with the HDS.
25. Do the ECM idle learn procedure.
26. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle.
27. Test-drive under these conditions:
- ECT SENSOR 1 above 176 F (80 degrees C)
- Transmission in 4th gear
- Engine speed between 1,500-3,000 rpm
- Drive about 1 minute or more

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

Are any Temporary DTCs or DTCs indicated?

YES - If DTC P0138 is indicated, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.

NO - Go to step 29.

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

Does the screen indicate PASSED?

YES - Troubleshooting is complete.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM, 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 20 and recheck.

30. Update the ECM if it does not have the latest software, or substitute a known-good ECM.
31. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle.
32. Test-drive under these conditions:
- ECT SENSOR 1 above 176 F degrees (80 C degrees)
- Transmission in 4th gear
- Engine speed between 1,500-3,000 rpm
- Drive 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 ECM. If the ECM was updated, substitute a known-good ECM, then go to step 31. If the ECM was substituted, go to step 1.

NO - If no Temporary DTCs or DTCs are indicated, go to step 34. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.

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

Does the screen indicate PASSED?

YES - If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM. If the ECM was updated, substitute a known-good ECM, then go to step 31. If the ECM 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 and recheck.