P0138
DTC P0138: Secondary HO2S (Sensor 2) Circuit High Voltage1. Reset the ECM.
2. Start the engine. Hold the engine at 3,000 rpm with no load (in neutral) until the radiator fan comes on.
3. Check the secondary HO2S (Sensor 2) output voltage at 3,000 rpm with a scan tool or the HDS.
Does the voltage stay at 0.6 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 secondary HO2S (Sensor 2) output voltage with a scan tool or the HDS.
Is there 0.6 V or more?
YES - Go to step 9.
NO - Replace the secondary HO2S (Sensor 2).
9. Turn the ignition switch OFF.
10. Connect ECM connector terminals C15 and C18 with a jumper wire.
11. Turn the ignition switch ON (II).
12. Check the secondary HO2S (Sensor 2) output voltage with a scan tool or the HDS.
Is there 0.6 V or more?
YES - Substitute a known-good ECM and recheck. If the symptom/indication goes away, replace the original ECM.
NO - Repair open in the wire between the ECM (C15, C18) and the secondary HO2S (Sensor 2).