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Home >> Toyota >> 1999 >> Avalon XLS >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock Brake System W/Traction Control System >> Diagnostic Tests >> DTC 49: Stoplight Switch Circuit >> Diagnostic Procedure

Diagnostic Procedure

  1. Depress brake pedal and ensure stoplights illuminate. If stoplights illuminate, go to next step. If stoplights do not illuminate, check stoplight switch adjustment. See STOPLIGHT SWITCH  under ADJUSTMENTS. If adjustment is okay, diagnose and repair stoplight switch circuit. See WIRING DIAGRAMS .
  2. Turn ignition off. Remove ABS/TRAC ECU. Do not disconnect electrical connectors. Measure voltage between ground and ABS/TRAC ECU terminal STP (connector terminal A34-16) when brake pedal is depressed. See Figure. If voltage is 8-14 volts, replace ABS/TRAC ECU. If voltage is not 8-14 volts, go to next step.
  3. Check for open circuit in wiring harness between stoplight switch and ABS/TRAC ECU terminal STP (connector terminal A34-16). See WIRING DIAGRAMS . Repair as necessary. If wiring harness is okay, replace ABS/TRAC ECU.
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