DTC Troubleshooting

DTC Troubleshooting: P0139, P0159

DTC P0139:

Rear Secondary HO2S (Bank 1, Sensor 2) Slow Response

DTC P0159:

Front Secondary HO2S (Bank 2, Sensor 2) Slow Response

NOTE:

- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information Initial Inspection and Diagnostic Overview.
- Information marked with an asterisk (*) applies to the front bank (Bank 2).

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 P or N) until the radiator fan comes on, then let it idle.

4. Test-drive under these conditions:

- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in D
- Drive at a steady speed between 55-75 mph (88-120 km/h) for 1 minute, then decelerate (with the throttle fully closed) for 10 seconds.

5. Monitor the OBD STATUS for DTC P0139 and/or P0159* 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 secondary HO2S (Sensor 2) and the PCM. 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 to LOCK (0).

7. Replace secondary HO2S (Sensor 2) Secondary HO2S Replacement.

8. Turn the ignition switch to ON (II).

9. Reset the PCM with the HDS.

10. Do the PCM idle learn procedure PCM Idle Learn Procedure.

11. Start the engine, and let it idle without load (in P or N) until the radiator fan comes on.

12. Test-drive under these conditions:

- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in D
- Drive at a steady speed between 55-75 mph (88-120 km/h) for 1 minute, then decelerate (with the throttle fully closed) for 10 seconds.

13. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0139 and/or P0159* indicated?

YES -

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

NO -

Go to step 14.

14. Monitor the OBD STATUS for DTC P0139 and/or P0159* in the DTCs MENU with the HDS.

Does the screen indicate PASSED?

YES -

Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step 13, go to the indicated DTC's troubleshooting.�

NO -

If the screen indicates FAILED, check for poor connections or loose terminals at 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 11.