DTC Troubleshooting

Control System DTCs

DTC Troubleshooting: P0137

DTC P0137 : Secondary HO2S (Sensor 2) Circuit Low Voltage

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information How To Troubleshoot The Fuel And Emissions Systems.

1. Problem verification:

Problem verification
-1. Turn the ignition switch to ON (II).

-2. Clear the DTC with the HDS.

-3. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on.

-4. Monitor the OBD STATUS for DTC P0137 in the DTCs MENU with the HDS.

Does the HDS indicate FAILED?
-YES- The failure is duplicated. Go to step 2.
-NO- If the HDS indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at secondary HO2S (Sensor 2) and the ECM. If the HDS indicates EXECUTING, keep idling until a result comes on. If the HDS indicates OUT OF CONDITION, go to step 1-3 and recheck.

2. Shorted wire check (SO2_SG line):

Shorted wire check (SO2_SG line)
-1. Turn the ignition switch to LOCK (0).

-2. Jump the SCS line with the HDS.

-3. Disconnect the following connector.





-4. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- Repair a short in the SO2_SG wire between the ECM (C47) and secondary HO2S (Sensor 2), then do the repair verification.
-NO- The SO2_SG wire is not open. Go to step 3.

3. Shorted wire check (SO2 line):

Shorted wire check (SO2 line)
-1. Disconnect the following connector.





-2. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- Repair a short in the SO2 wire between the ECM (B46) and secondary HO2S (Sensor 2), then do the repair verification.
-NO- The SO2 wire is OK. Update the ECM ECM/PCM Update if it does not have the latest software, or substitute a known-good ECM Service and Repair, then do the repair verification.

Repair verification (OBD STATUS check):

-1. Reconnect all connectors.

-2. Turn the ignition switch to ON (II).

-3. Reset the ECM with the HDS How To Troubleshoot The Fuel And Emissions Systems.

-4. Do the ECM idle learn procedure. ECM/PCM Idle Learn Procedure

-5. Start the engine, and let it idle without load (in neutral) until the radiator fan comes on, then let it idle.

-6. Monitor the OBD STATUS for DTC P0137 in the DTCs MENU with the HDS.

Does the HDS indicate PASSED, FAILED, EXECUTING, or OUT OF CONDITION?
-PASSED- Troubleshooting is complete. If the ECM was substituted, replace the original ECM Service and Repair. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.
-FAILED- Go to step 1 and recheck. If the ECM was updated, substitute a known-good ECM Service and Repair, then check the OBD STATUS again.
-EXECUTING- Keep the test condition until a result comes on.
-OUT OF CONDITION- Meet the test condition, and check the OBD STATUS again.