## DTC Troubleshooting: P0137 (63-1)

DTC P0137 (63-1): | Secondary HO2S (Sensor 2) Circuit Low Voltage

1. | Reset the ECM/PCM.

2. | Start the engine. Hold the engine at 3,000 rpm (min-1) 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 (min-1) with the HDS or the scan tool. Is there 0.3 V or less? YES - Go to 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/PCM.n

4. | Turn the ignition switch OFF.

5. | Disconnect the secondary HO2S (Sensor 2) 4P connector.

6. | Turn the ignition switch ON (II).

7. | Check the secondary HO2S (Sensor 2) output voltage with the HDS or the scan tool. Is there 0.3 V or less? YES - Go to 8. NO - Replace the secondary HO2S (Sensor 2).n

8. | Turn the ignition switch OFF.

9. | Disconnect ECM/PCM connector E (31P).

10. | Check for continuity between the secondary HO2S (Sensor 2) 4P connector terminal No. 2 and body ground. Is there continuity? YES - Repair short in the wire between the ECM/PCM (E2) and the secondary HO2S (Sensor 2).n NO - 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.n