P0138
DTC P0138: Secondary HO2S (Sensor 2) Circuit High Voltage1. 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 mare?
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 the right side of the dash), C104 (located at the right 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 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 A23 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 (A23 or C18) and the secondary HO2S (Sensor 2).