Sensor Inspection

NOTE: Refer to "SIGNAL WAVEFORM & DATA " in the "General Information" procedure

Visually/physically inspect the HO2S for the following conditions:
- Ensure that the HO2S is securely installed.
- Silicon contamination. This contamination will be indicated by a white powdery coating on the portion of the sensor exposed to the exhaust stream and this will result in a but false (high) voltage signal
- Fuel, engine coolant or oil contamination
- Use of improper sealant
- If contamination is evident on the HO2S, Fix the source of the sensor contamination before replacing the sensor to prevent future contamination. Go to "VERIFICATION OF VEHICLE REPAIR " procedure.
Visually/physically inspect the MAFS for the following conditions:
- Contamination or deterioration
- Poor connection or damaged harness
Check for an intermittent TPS false signal. TPS signal displayed on a scantool should increase steadily when depressing accelerator pedal after starting.
Verify that the ECM ground connections are clean and properly tightened.
If test result is NG, repair or replace as necessary and go to "VERIFICATION OF VEHICLE REPAIR " procedure.
If OK, go to POSITIVE CRANKCASE VENTILATION SYSTEM INSPECTION .

NOTE: If the contamination is evident on the HO2S or MAFS. Fix the source of the sensor contamination before replacing the sensor to prevent future contamination.