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- Check if stoplights are functioning correctly. If stoplights function correctly, go to next step. If stoplights do not function correctly, check stoplight circuit and repair as necessary.
- Ensure ignition is off. Disconnect ECU wiring harness connector. Using DVOM, measure voltage between terminal No. 29 (Green wire) and ground while depressing brake pedal. See Figure. If battery voltage is not present, repair or replace wiring harness between stoplight switch and ECU. If battery voltage is present, stoplight switch circuit is okay. Replace faulty ECU.