DTC Troubleshooting
DTC Troubleshooting: 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. Initial Inspection and Diagnostic Overview
1. Turn the ignition switch to 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 1.27 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 to LOCK (0).
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 to ON (II).
9. Check the HO2S S2 in the DATA LIST with the HDS.
Does the voltage stay at 1.27 V or more?
YES - Go to step 10.
NO - Go to step 19.
10. Turn the ignition switch to LOCK (0).
11. Remove the jumper wire from the secondary HO2S (Sensor 2) 4P connector.
12. Connect secondary HO2S (Sensor 2) 4P connector terminal No. 2 to body ground with a jumper wire.
13. Turn the ignition switch to ON (II).
14. Check the HO2S S2 in the DATA LIST with the HDS.
Does the voltage stay at 1.27 V or more?
YES - Go to step 15.
NO - Repair open in the wire between the ECM (A23) and the secondary HO2S (Sensor 2), then go to step 21.
15. Turn the ignition switch to LOCK (0).
16. Jump the SCS line with the HDS.
17. Disconnect ECM connector E (31P).
18. Check for continuity between ECM connector terminal E20 and body ground.
Is there continuity?
YES - Go to step 29.
NO - Repair open in the wire between the ECM (E20) and the secondary HO2S (Sensor 2), then go to step 21.
19. Turn the ignition switch to LOCK (0).
20. Replace the secondary HO2S (Sensor 2). Secondary HO2S Replacement
21. Reconnect all connectors.
22. Turn the ignition switch to ON (II).
23. Reset the ECM with the HDS.
24. Do the ECM idle learn procedure. ECM Idle Learn Procedure
25. Start the engine, and let it idle without load (in neutral) until the radiator fan comes on.
26. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 176 °F (80 °C)
- Transmission in 4th
- Engine speed at 1,500-3,000 rpm
- Drive 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 ECM, then go 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 DTC's troubleshooting.
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 25.
29. Reconnect all connectors.
30. Update the ECM if it does not have the latest software, ECM Update or substitute a known-good ECM. Initial Inspection and Diagnostic Overview
31. Start the engine, and let it idle without load (in neutral) until the radiator fan comes on.
32. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 176 °F (80 °C)
- Transmission in 4th
- Engine speed at 1,500-3,000 rpm
- Drive 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, Initial Inspection and Diagnostic Overview then go to step 32. If the ECM 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 ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. Service and Repair If any other Temporary DTCs or DTCs were indicated in step 33, go to the indicated DTC's troubleshooting.
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, Initial Inspection and Diagnostic Overview 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.