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Home >> Volvo >> 1987 >> 780 AW71 >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock Brake System >> Testing >> Circuit Tests >> ECU Power Circuits

ECU Power Circuits

  1. Turn ignition switch to the "ON" position. Connect negative lead of voltmeter to a good ground. Battery voltage should be present at terminals No. 1, 7, 9, 27 and 28. If there is no voltage present at:
    • 1 - Transient surge protector is defective.
    • 7 - ABS converter is defective.
    • 9 - ABS converter is defective.
    • 27 - Solenoid valve relay is defective.
    • 28 - Pump motor relay is defective.
  2. If voltage at terminal No. 27 is correct (battery voltage), voltage at terminal No. 29 should be 0.5-1.0 volt. If voltage at terminal No. 29 is not correct, solenoid valve relay is defective.
  3. Depress brake pedal and check terminal No. 25. Battery voltage should be present. If voltage is not correct, check stoplight switch. Replace if defective.
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