## DTC Troubleshooting: P0138 (63-2)

DTC P0138 (63-2): | Secondary HO2S(Sensor 2) Circuit High Voltage

1. | Reset the ECM/PCM.

2. | Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on.

3. | Check the secondary HO2S (Sensor 2) output voltage at 3,000 rpm (min-1) with the HDS or the scan tool. Is there 1.0 V or more? YES - Go to 4. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the at ECM/PCM.n

4. | Turn the ignition switch OFF.

5. | Disconnect the secondary HO2S (Sensor 2) 6P connector.

6. | Connect secondary HO2S (Sensor 2) 6P connector terminals No. 1 and No. 2 with a jumper wire.

7. | Turn the ignition switch ON (II).

8. | Check the secondary HO2S (Sensor 2) output voltage with the HDS or the scan tool. Is there 1.0 V or more? YES - Go to 9. NO - Replace the secondary HO2S (Sensor 2).n

9. | Turn the ignition switch OFF.

10. | Connect ECM/PCM connector terminalsE2 and E4 with a jumper wire.

11. | Turn the ignition switch ON (II).

12. | Check the secondary HO2S (Sensor 2) output voltage with the HDS or the scan tool. Is there 1.0 V or more? YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/ PCM.n NO - Repair open in the wire between the ECM/PCM (E2, E4) and the secondary HO2S (Sensor 2).n