| WARNING | Read service precautions before proceeding with service procedure. See SERVICE PRECAUTIONS . |
| CAUTION | If Engine Control Module (ECM) replacement is instructed in following test, always ensure ECM electrical connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. |
Circuit Description
Heated oxygen sensor No. 2 monitors exhaust gas oxygen content and delivers input signals to ECM. Heated oxygen sensor No. 2 is located on exhaust pipe behind catalytic converter and may also be referred to as bank No. 1 sensor No. 2, or rear oxygen sensor. ECM uses input signals to determine fuel injection system operation. DTC is set when heated oxygen No. 2 heater current draw exceeds 2 amps or is .2 amp or less when heater operates. If DTC P0141 exists, ECM will operate in fail-safe mode which turns off the heater for oxygen sensor No. 2. Possible causes are
- Heater circuit for heated oxygen sensor No. 2 is open or shorted.
- Defective heated oxygen sensor No. 2.
- 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.