DTC Troubleshooting

DTC P0139: Secondary HO2S (Sensor 2) Slow Response

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. Test-drive under these conditions:
- ECT SENSOR 1 above 176 °F (80 °C)
- Transmission in 4th gear
- Vehicle speed at 35 mph (56 km/h) or more
- Drive 50 seconds

5. Monitor the OBD STATUS for DTC P0139 in the DTCs MENU with the HDS.

Does the screen indicate FAILED?

YES - Go to step 6.

NO - If the screen indicates PASSED, 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. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, Go to step 3 and recheck.

6. Turn the ignition switch OFF.
7. Replace the secondary HO2S (Sensor 2).
8. Turn the ignition switch ON (II).
9. Reset the ECM with the HDS.
10. Do the ECM idle learn procedure.
11. 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.

12. Test-drive under these conditions:
- ECT SENSOR 1 above 176 °F (80 °C)
- Transmission in 4th gear
- Vehicle speed at 35 mph (56 km/h) or more
- Drive 50 seconds

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

Is DTC P0139 indicated?

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

NO - Go to step 14.

14. Monitor the OBD STATUS for DTC P0139 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 13, 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 ECM. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, Go to step 12.