Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Toyota Tundra. However, it is still accessible from the selected car via links, so may be relevant.
- Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. See Figure. Turn ignition on. Using voltmeter, check voltage between body ground and terminal No. 9 (Red/White wire) at ECM electrical connector E4. See Figure. This is the HTS terminal on ECM. Voltage should be 9-14 volts. If voltage is not within specification, go to next step. If voltage is within specification, replace ECM.
- Disconnect electrical connector for heated oxygen sensor. Heated oxygen sensor is located on exhaust pipe, behind catalytic converter. Using ohmmeter, check resistance between +B and HT terminals on electrical connector for heater on heated oxygen sensor. See Fig 1. Resistance should be 11-16 ohms at 68°F (20°C) and 23-32 ohms at 1472°F (800°C). If resistance is within specification, go to next step. If resistance is not within specification, replace heated oxygen sensor. See HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
- Check for defective wiring harness and electrical connectors between ECM and heated oxygen sensor, and between heated oxygen sensor and EFI main relay. See WIRING DIAGRAMS article. EFI main relay may also be referred to as EFI relay. EFI main relay is located in fuse/relay box at driver's side front corner of engine compartment.