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Home >> Mazda >> 1994 >> MX-3 Base, Automatic >> Repair and Diagnosis (Single Page) >> Brakes >> Anti-Lock Brakes >> Anti-Lock Brake System >> Trouble Shooting >> Pre-Diagnosis Trouble Shooting >> ABS Warning Light Illuminates Constantly After Engine Starts

ABS Warning Light Illuminates Constantly After Engine Starts

  1. Check for ABS DTCs. See RETRIEVING DTC under DIAGNOSIS & TESTING. If no DTCs are present, start engine and let idle.
  2. Using voltmeter, check voltage at alternator terminals "B", "L" and "S". See Figure . Voltmeter should indicate battery voltage. If voltmeter indicates battery voltage, go to next step. If voltmeter does not indicate battery voltage, repair alternator.
    NOTE: If battery voltage is low, ABS warning light may illuminate.
  3. Start engine. Check voltage at battery and ABS control unit connector terminal 1H (Red/White wire). If battery voltage is less than 10 volts, charge or replace battery.
  4. If battery voltage is greater than 10 volts and voltage at ABS control unit connector terminal 1H (Red/White wire) is less than 10 volts, check wiring harness between battery and ABS control unit connector terminal 1H (Red/White wire). Repair as necessary. If wiring harness is okay, go to next step.
  5. Check wiring harness between the following:
    • ABS control unit and fail-safe relay.
    • ABS warning light and ABS control unit.
    • ABS warning light and fail-safe relay.

    Repair as necessary. If wiring harnesses are okay, go to next step.

  6. Ground ABS control unit 18-pin connector terminal 2J (Black/Blue wire). Turn ignition on. Listen for operation of fail-safe relay, ensure ABS warning light is not illuminated, and ABS control unit terminal 1D (Brown wire) indicates 12 volts. See Figure .
  7. If fail-safe relay, ABS warning light and ABS control unit connector terminal voltage are as indicated, go to next step. If fail-safe relay, ABS warning light and ABS control unit terminal voltage are not as indicated, check fail-safe relay. Also check wiring harness between fail-safe relay, ABS control unit and battery, and between fail-safe relay and hydraulic unit.
  8. Check voltage at ABS control unit 12-pin connector terminals 1E (Black wire), 1F (Black wire) and 1H (Red/White wire). Also check voltage at ABS control unit 18-pin connector terminals 2B (Green/Red wire) and 2L (Blue/Yellow wire). See Figure .
  9. If voltages are as specified, replace ABS control unit. If voltages are not as specified, check wiring harness between ABS control unit and the following:
    • Ground
    • Ignition Switch
    • Diagnosis Connector
    • ABS Warning Light
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