| CAUTION | If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. |
Note. Heated oxygen sensor No. 1 is located on exhaust pipe in front of catalytic converter and may be referred to as bank No. 1 sensor No. 1.
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 fuel injector.
- Defective ECM.
Diagnostic Aids
Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.