## 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 scan tool. Does the voltage stay at 0.3 V or less? YES - Go to 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.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 scan tool. Does the voltage stay at 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 the negative cable from the battery.

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

11. | 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 - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original ECM/ PCM.n