P0138

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

1. Reset the ECM with the HDS.
2. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on.
3. Check the HO2S S2 at 3,000 rpm in the DATA LIST with the HDS.

Does the voltage stay at 4.0 V or more?

YES - Go to step 4.

N0 - Intermittent failure, system is 0K at this time. Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the ECM.

4. Turn the ignition switch 0FF.
5. Disconnect the secondary HO2S (Sensor 2) 4P connector.




6. Connect secondary HO2S (Sensor 2) 4P connector terminals No.1 and No.2 with a jumper wire.
7. Turn the ignition switch 0N (II).
8. Check the HO2S S2 in the DATA LIST with the HDS.

Is there 4.0 V or more?

YES - Go to step 9.

N0 - Replace the secondary HO2S (Sensor 2).

9. Turn the ignition switch 0FF.
10. Disconnect the jumper wire.




11. Connect ECM connector terminals C31 andC18 with a jumper wire.
12. Turn the ignition switch 0N (II).
13. Check the HO2S S2 in the DATA LIST with the HDS.

Is there 4.0 V or more?

YES - Substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM.

N0 - Go to step 14.

14. Turn the ignition switch 0FF.
15. Disconnect the jumper wire.




16. Connect secondary HO2S (Sensor 2) 4P connector terminal No.2 to body ground with a jumper wire.
17. Check the HO2S S2 in the DATA LIST with the HDS.

Is there 4.0 V or more?

YES - Repair open in the wire between the ECM (C31 land the secondary HO2S (Sensor 2).

N0 - Go to step 18.

18. Turn the ignition switch 0FF.
19. Disconnect the jumper wire.
20. Disconnect ECM connector C (31P).




21. Connect secondary HO2S (Sensor 2) 4P connector terminal No.1 to body ground with a jumper wire.




22. Check for continuity between ECM connector terminal C18 and body ground.

Is there continuity?

YES - Substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM.

N0 - Repair open in the wire between the ECM (C18) and the secondary HO2S (Sensor 2).