DTC Confirmation Test (Overall Function Check)
NOTE:
Use the following test to check closed-loop fuel control. During this test, DTC may not be confirmed.
Malfunction is detected when ECM does not operate in closed loop. Possible causes are:
- Front HO2S circuit open or shorted.
- Defective front HO2S.
- Defective front HO2S heater.
CAUTION:
DO NOT use ECM ground terminals when measuring voltage.
To check closed-loop operation, start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal 62 (front HO2S signal), by backprobing. See Figure and Figure . Monitor voltmeter with engine at 2000 RPM. Voltage should be less than .21 volt at least once and more than .70 volt at least once.