Anti-Lock Braking System (ABS) - Except Evolution: Overview Mitsubishi Lancer IX

GENERAL DESCRIPTION

ABS has been adopted as optional equipment in vehicles to maintain directional stability and steering performance during sudden braking.

The ABS control method used is a 4-sensor, 4-channel method which provides independent control for all wheels. The system has the following features.

ABS Operation Sounds and Sensations

During normal operation, the ABS makes several sounds that may seem unusual at first

1. A whining sound is caused by the ABS hydraulic unit motor.
2. When pressure is applied to the brake pedal, the pulsation of the pedal causes a scraping sound.
3. When the brakes are applied firmly, the ABS operates, rapidly applying and releasing the brakes many times per second. This repeated application and release of braking forces can cause the suspension to make a thumping sound and the tires to squeak.

INTRODUCTION TO ANTI-LOCK BRAKING SYSTEM DIAGNOSIS

The anti-lock brake system (ABS) operates differently from conventional brake systems. These differences include sounds, sensations, and vehicle performance that owners and service technicians who are not familiar with ABS may not be used to.

By Special Operation for Brake Pedal

Required Special Tool

1. MB991529: Diagnostic Trouble Code Check Harness

Scheme 249

Scheme 250

1. Use special tool MB991529 to ground number 1 terminal of the data link connector. NOTE: If the ABS-ECU functions have stopped due to the fail-safe function, the diagnostic trouble code cannot be erased.
2. Depress the brake pedal and hold it.
3. Turn the ignition switch to the "ON" position.
4. After turning the ignition switch to the "ON", release the pedal within three seconds. Repeat this process of pressing and releasing the brake pedal 10 continuous times.
5. Turn the ignition switch to the "LOOK" (OFF) position.
6. Disconnect special tool MB991529.

CIRCUIT OPERATION

1. A toothed ABS rotor generates a voltage pulse as it moves across the pickup field of each wheel speed sensor.
2. The amount of voltage generated at each wheel is determined by the clearance between the ABS rotor teeth and the wheel speed sensor, and by the speed of rotation.
3. The wheel speed sensors transmit the frequency of the voltage pulses and the amount of voltage generated by each pulse to the ABS electronic control unit (ABS-ECU).
4. The ABS hydraulic unit modulates the amount of braking force individually applied to each wheel cylinder.

The ABS-ECU power is supplied to the ABS-ECU (terminal 20) from the ignition switch (1G2) through the multi-purpose fuse number 12 in the junction block.

The "ON" signal when the brake pedal is pressed or the "OFF" signal when the brake pedal is released is input to the ABS-ECU (terminal 3).

Power is continuously supplied to the ABS-ECU through fusible link number 3 to operate the solenoid valve and motor.

1. The DTC is set by the ABS-ECU (terminal 13) to the diagnostic output terminal (terminal 7) of the data link connector.
2. When the data link connector's diagnostic test mode control terminal (terminal 1) is grounded, the ABS-ECU will go into diagnostic mode.

TECHNICAL DESCRIPTION (COMMENT)

When communication with the scan tool is not possible, the cause is probably an open circuit in the ABS-ECU power circuit or an open circuit in the diagnostic output circuit.

1. The ABS warning light power is supplied from the ignition switch. The ABS-ECU grounds the circuit to illuminate the light.
2. The ABS-ECU illuminates the ABS warning light for 3 seconds while running self-check. This light can be illuminated for 3 seconds upon start-up or when the ignition switch is turned to the "ON" position with engine stopped.
3. When the ABS-ECU connector is disconnected, the circuit is grounded to illuminate the light by the ABS warning light relay ON operation.
4. The ABS-ECU controls the continuity to the ABS warning light by turning the power transistor in the unit "OFF" and "ON" to turn the ABS warning light relay "ON" and "OFF", respectively.

The cause may be: an open circuit in the ABS warning light power supply circuit, a blown ABS warning light bulb, or a short circuit to ground between the ABS warning light and the ABS-ECU.

Refer to INSPECTION PROCEDURE 2: WHEN THE IGNITION KEY IS TURNED TO "ON" (Engine Stopped), the ABS Warning Light does not Illuminate.

The cause is probably the ABS-ECU malfunction.

The cause depends on driving and road surface conditions, so diagnosis may be difficult. However, if no diagnostic trouble code is displayed, carry out the following inspection.