P0138
DTC P0138: Secondary HO2S (Sensor 2) Circuit High Voltage1. Reset the ECM/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 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 wires at the secondary HO2S (Sensor 2), and at the ECM/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 1.0 V or more?
YES - Go to step 9.
NO - Replace the secondary HO2S (Sensor 2).
9. Turn the ignition switch OFF.
10. Connect ECM/PCM connector terminals E2 and E4 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 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.
NO - Repair open in the wire between the ECM/PCM (E2, E4) and the secondary HO2S (Sensor 2).