Diagnosis & Repair (Using Hand-Held Tester)
WARNING: This page is about a different car, the 2003 Lexus SC 430. 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. If okay, go to next step. If not okay, repair stop light circuit.
- If using hand-held tester, connect the hand-held tester to the DLC3. Turn the ignition switch ON and push the hand-held tester ON. Read the STP signal on the hand-held tester. With brake pedal depressed, STP signal should be ON. With brake pedal released, STP signal should be OFF. If okay, check for intermittent problems. If not okay, go to next step.
- Disconnect the D2 driver side junction block ECU 18-pin connector. See Fig 1. Disconnect the ECM E5 connector. See Fig 2. Check continuity between the wire harness side connectors. See DRIVER SIDE JUNCTION BLOCK/ECM CONTINUITY table. If continuity is to specification, check and replace ECM. If continuity is not to specification, repair or replace harness or connector as necessary.
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
DRIVER SIDE JUNCTION BLOCK/ECM CONTINUITYTerminals Specification STPO (D2-12) - STP (E5-4) Continuity STPO (D2-12) Or STP (E5-4) - E1 (E3-7) No Continuity - Check stop light switch by measuring voltage between ECM terminals E1 and STP. See CHECKING STOP LIGHT SWITCH . See Fig 3. Replace stop light switch as necessary. If okay, go to next step.CHECKING STOP LIGHT SWITCH
Brake Pedal Position Voltage Depressed 7.5-14 Released Less Than 1.5 - Check harness and connector between ECM and stop light switch. Repair as necessary. If okay, replace ECM.