Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
- Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector. If DTC P0135 is set, measure voltage between ground and terminal No. 4 (Red wire) at ECM harness connector E7. If DTC P0155 is set, measure voltage between ground and terminal No. 3 (Yellow wire) at ECM harness connector E7. See Figure. Voltage should be 9-14 volts at each terminal. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
- Disconnect suspect heated oxygen sensor No. 1 harness connector. Measure resistance between terminals B+ (Black/Yellow wire) and HT (Red wire on bank No. 1, or Yellow wire on bank No. 2) at heated oxygen sensor connector (component side). See Fig 1. Resistance should be 11-16 ohms at 68°F (20°C). If resistance is not as specified, replace appropriate heated oxygen sensor No. 1. If resistance is as specified, go to next step.
- Repair wiring between ECM and appropriate heated oxygen sensor or between appropriate heated oxygen sensor and EFI main relay. See WIRING DIAGRAMS article.