| CAUTION | If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Note. Heated oxygen sensor No. 1 refers to oxygen sensor closest to engine block. Heated oxygen sensor No. 2 refers to oxygen sensor farthest from engine block.
Circuit Description
Heated oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to determine fuel injection system operation. DTC is set when heated oxygen sensor No. 1 voltage remains at .4 volt or more, or .55 volt or less during idle, once engine is at normal operating temperature. Possible causes are
- Heated oxygen sensor No. 1 circuit is open or shorted.
- Defective heated oxygen sensor No. 1.
- Air induction malfunction.
- Improper fuel pressure.
- Defective injector.
- Vehicle has run out of fuel.
- Defective ECM.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.