Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.
- Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure.
- Turn ignition on. For DTC P0135, using voltmeter, check voltage between body ground and terminal No. 4 (Red wire) at ECM electrical connector E6. See Figure. This is the HTL terminal on ECM. For DTC P0155, using voltmeter, check voltage between body ground and terminal No. 3 (Yellow wire) at ECM electrical connector E6. See Figure. This is the HTR terminal on ECM. On either DTC, 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 appropriate heated oxygen sensor located on exhaust manifold. Heated oxygen sensor (bank No. 1 sensor No. 1) is located on driver's side exhaust manifold and heated oxygen sensor (bank No. 2 sensor No. 1) is located on passenger's side exhaust manifold.
- Using ohmmeter, check resistance between +B and HT terminals on electrical connector for heater on appropriate heated oxygen sensor. See Fig 1. Resistance should be 11-16 ohms at 68°F (20°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 wiring harness and electrical connectors between ECM and appropriate heated oxygen sensor, and between appropriate 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.