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Home >> Lexus >> 2000 >> LX 470 >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock Brake System >> Diagnostic Tests >> DTC 49: Stoplight Switch Circuit >> Diagnostic Procedure

Diagnostic Procedure

  1. Ensure stoplights illuminate when brake pedal is depressed and turns off when released. If operation is as specified, go to next step. If operation is not as specified, repair stoplight circuit. See WIRING DIAGRAMS .
  2. Remove ABS ECU, leaving harness connectors connected. Using DVOM, check voltage (backprobe) between chassis ground and STP terminal on ABS ECU harness connector. Depress brake pedal. If voltage reading is 8-14 volts, inspect applicable harness connectors. Ensure connections are clean and tight. Repair as necessary. If voltage reading is not 8-14 volts, go to next step.
  3. Check for open circuit in wiring harness between ABS ECU and stoplight switch. See WIRING DIAGRAMS . Repair as necessary. If no problem is found, replace ABS ECU.
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