ULEV Model

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

(ULEV model)

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 in the DATA LIST with the HDS.

Does the voltage stay at 1.0 V or more?

YES - Go to step 4.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and at the ECM.

4. Turn the ignition switch OFF.
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 ON (II).
8. Check the HO2S S2 in the DATA LIST with the HDS.

Is there 0.6 V or more?

YES - Go to step 9.

NO - Replace the secondary HO2S (Sensor 2) and the third HO2S (Sensor 3).

9. Turn the ignition switch OFF.




10. Connect ECM connector terminals A10 and A25 with a jumper wire.
11. Turn the ignition switch ON (II).
12. Check the HO2S S2 in the DATA LIST with the HDS.

Is there 0.6 V or more?

YES - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.

NO - Repair open in the wire between the ECM (A10, A25) and the secondary HO2S (Sensor 2).