Diagnosis & Repair
WARNING: This page is about a different car, the 2003 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
- Check if the stop lights go on and off normally when the brake pedal is operated and released. Repair stop light circuit as necessary. If stop lights operate okay, go to next step.
- Connect the hand-held tester to the DLC3. Turn the ignition switch ON and push the hand-held tester main switch ON. Read STP signal on the hand-held tester. With brake pedal depressed, STP signal is ON. With brake pedal released, STP signal is OFF. When not using hand-held tester, turn the ignition switch ON. Check the voltage between terminal STP of the ECM connector and body ground. See Fig 1. With brake pedal depressed, voltage should be 7.5-14 volts. With brake pedal released, voltage should be less than 1.5 volts. If okay, check for intermittent problems. If not okay, go to next step.
- Check harness and connector between ECM and stop light switch. Repair or replace harness or connector. If okay, check and replace ECM.