Diagnostic Aids
Check for:
- Rich Exhaust
If Codes P0131, P0132 or P0134 are present, diagnose these codes prior to Code P0138. An overly rich exhaust may load catalyst causing high sensor No. 2 signal voltages.
- False rich indication due to silicone contamination of sensor No. 2. This will be indicated by Code P0138 accompanied by a powdery White deposit on sensor.
- Faulty sensor No. 2 (Catalyst Monitor)
If sensor No. 2 is internally shorted, sensor No. 2 voltage displayed on scan tester will be greater than one volt.
- Intermittent Test
Observe sensor No. 2 on scan tester while moving related connectors and wiring harness with ignition on. If failure is induced, sensor No. 2 display will change. This may assist in isolating location of malfunction.
- Damaged Harness
Inspect PCM harness for a short to voltage in signal circuit.