Diagnostic Aids

Check for the following conditions:

• The HO2S 2 input voltage on a cold sensor, ignition ON with the engine OFF, is approximately 55 mV.
• Inspect the wiring harness for damage. If the harness appears to be OK, observe the HO2S 2 display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the HO2S 2 display will indicate the location of the fault.
• If a DTC P0138 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Heated Oxygen Sensor/Oxygen Sensor System Set .
• An intermittent malfunction may be caused by fault in the HO2S circuit sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .
• Repair any electrical circuit faults that were found. Refer to Wiring Repairs .

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.