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Home >> Volvo >> 1989 >> 740 GL, 4D Sedan, Standard >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock Brake System >> Testing >> Ecu Power Circuit Test >> ECU Power Circuits

ECU Power Circuits

  1. Turn ignition on. Connect negative lead of DVOM to ground. Check for voltage at terminal No. 25 (while depressing brake pedal), 27, 28 and 29 of ECU connector. All terminals should have battery voltage present except for terminal No 29. Terminal No. 29 should have .5-1.0 volt.
  2. If there is no voltage present at terminal Nos.:
    • 25 - Check brake light switch; replace if defective.
    • 27 - Replace defective solenoid relay.
    • 28 - Replace defective pump relay.
    • 29 - If voltage reading at terminal No. 27 is correct, voltage at terminal No. 29 should be .5-1.0 volt. If voltage at terminal No. 29 is not correct, replace solenoid relay.
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