Mazda MX-3 silhouetteMX-3

ANTI-LOCK BRAKE SYSTEM

P-69prose procedure

ABS HYDRAULIC UNIT

The ABS control module contains a self-diagnostic function to check the hydraulic system operation. During the diagnostic mode, the ABS control module activates the ABS hydraulic unit to reduce the hydraulic pressure of the right front, left front, right rear, left rear in sequence for 0.5 second each at intervals of 1.5 seconds.

Inspection

  1. 1
    Verify that the battery is fully charged. Verify that the ABS warning light goes out after the engine is started.
  2. 2
    If the light stays ON after the engine has started, the ABS control module detects a failure and will not activate the hydraulic unit.
  3. 3
    Turn off the engine.
  4. 4
    On level ground, jack up the vehicle and support it evenly on safety stands. Shift the transaxle to neutral or N range.
    Illustration of the MX-3 jacked up and supported evenly on four safety stands on level ground.
  5. 5
    Release the parking brake.
  6. 6
    Rotate the wheels by hand, and inspect for brake drag.
  7. 7
    Using a jumper wire, connect the TBS and GND terminals of the data link connector.
    Illustration of the DATA LINK CONNECTOR with a JUMPER WIRE installed between the TBS and GND terminals. Magnified inset shows the connector terminal layout with GND and TBS terminals identified.
  8. 8
    Depress the brake pedal, and have an assistant verify that the right front wheel will not turn.
    Illustration of a hand rotating a road wheel by hand, with a curved arrow indicating rotation direction.
  9. 9
    With the brake still depressed, turn the ignition switch ON and verify that the brake is released momentarily (approx. 0.5 sec.) and the wheel turns when pressure-reduction operates.
    Timing chart showing IGNITION SWITCH (ON/OFF) over time with 0.5 sec / 1.5 sec intervals, PRESSURE (LOW/NORMAL) pulses labeled RF, LF, RR, LR each lasting 0.5 sec at 1.5 sec intervals, and MOTOR (ON/OFF) trace.
  10. 10
    Check operation of the remaining wheels in order: left front, right rear, left rear.
  11. 11
    If Steps 8, 9 and 10 show correct operation, the following systems are OK: Brake piping to ABS hydraulic unit; Braking system, including ABS hydraulic unit; Electrical system in ABS hydraulic unit (solenoid, motor, etc.); ABS control module, its output system (solenoid, relay, etc.) and harness. The following are not checked with the above steps: Input system and harness of ABS control module; Fluid leakage; Intermittent failure.
  12. 12
    Replace the ABS hydraulic unit if necessary.
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