Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Lexus RX 300 and 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.

Check the ECM. Check that the engine starts normally. With this inspection, ECM can be diagnosed if it works normally or not. If the results are OK, go to the next step. If the results are not good, replace the ECM. See ENGINE CONTROL MODULE (ECM) under REMOVAL & INSTALLATION.
Check the wiring harness. Disconnect the connector B5 of the body ECU, E8 of the ECM and passenger door ECU.
1. Check the continuity between terminal No. 11 (MPX1) of the body ECU No. 1 and terminal No. 18 (MPX2) of the ECM. See CONNECTOR IDENTIFICATION .
2. Check the continuity between terminal No. 18 (MPX2) of the ECM and 10 (MPX1) of the passenger door ECU.
The results are OK if there is continuity in the wiring harness of both step (a) and (b), or either step (a) or (b). If there is an open in the wiring harness of either step (a) or (b), repair it. If the results are OK, replace the ECM. See ENGINE CONTROL MODULE (ECM) under REMOVAL & INSTALLATION. If the results are not good, repair or replace the wiring harness.