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Inspection 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.
  1. Check that the stop light comes ON when the brake pedal is depressed, and turns OFF when the brake pedal is released. If the results are OK, go to the next step. If the results are not OK, check the stop light system. See appropriate BODY CONTROL SYSTEM article in COMMUNICATION DEVICES.
  2. Check the input signal. See INPUT SIGNAL CHECK  under SELF-DIAGNOSTIC SYSTEM. Check the indicator light when the brake pedal is depressed. The results are OK if the indicator light goes OFF when the brake pedal is depressed (stop light switch ON). If the results are OK, proceed to the next circuit inspection of the symptom. See PROBLEM SYMPTOM INDEX  table. If the results are not OK, go to the next step.
  3. Remove the cruise control ECU with the connectors still connected. Turn the ignition switch ON. Connect the positive lead (+) to terminal No. 3 (STP) of the cruise control ECU connector and the negative (-) lead to body ground, when the brake pedal is depressed and released. See CONNECTOR IDENTIFICATION . The results are OK if the voltage is 10-14 volts when the pedal is depressed and below 1 volt when the pedal is released. If the results are OK, proceed to the next circuit inspection of the symptom. See PROBLEM SYMPTOM INDEX  table. If the results are not OK, go to the next step.
  4. Check for an open in the wiring harness and connectors between terminal No. 3 (STP) of the cruise control ECU and stop light switch. If the results are OK check and replace the cruise control ECU. See CRUISE CONTROL ECU  under REMOVAL & INSTALLATION. If the results are not OK, repair or replace the wiring harness or connector.
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