A/T Model

DTC P0138: High Voltage in Secondary HO2S (Sensor 2) Circuit - A/T Model

1. Reset the PCM.
2. Start the engine. Hold the engine at 3,000 rpm 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 with the scan tool.

Does the voltage stay at 0.8 V or more?

YES - Go to step 4.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at C204 (located under right side of dash), C102 (located at the left side of the engine compartment), the Secondary HO2S (Sensor 2) and the PCM.

4. Turn the ignition switch OFF.
5. Disconnect the Secondary HO2S (Sensor 2) 4P connector.




6. Connect the Secondary HO2S (Sensor 2) 4P 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 scan tool.

Is there 0.8 V or more?

YES - Go to step 9.

NO - Replace the Secondary HO2S (Sensor 2).

9. Turn the ignition switch OFF.




10. Connect PCM connector terminals A1 and C18 with a jumper wire.
11. Turn the ignition switch ON (II).
12. Check the Secondary HO2S (Sensor 2) output voltage with the scan tool.

Is there 0.8 V or more?

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

NO - Repair open in the wire between the PCM (A1, C18) and the Secondary HO2S (Sensor 2).