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Home >> Mitsubishi >> 2002 >> Lancer O-Z Rally Edition L4-2.0L SOHC >> Repair and Diagnosis >> Brakes and Traction Control >> Antilock Brakes / Traction Control Systems >> Electronic Brake Control Module >> Description and Operation >> Electronic Control Unit

Electronic Control Unit

ELECTRONIC CONTROL UNIT (ECU)
- The Electronic Control Unit (ECU) is integrated with the hydraulic unit. This makes it unnecessary to have drive signal harnesses for the solenoid valves pump motor, thus providing improved reliability.
- The ABS-ECU is equipped with a diagnostic function and a memory that a problem has occurred, it causes the fail-safe function to operate and the ABS warning light to illuminate.
- The ABS-ECU detects the vehicle speed by means of signals from the wheel speed sensors in order to determine the vehicle driving condition, and also predicts if any of the wheels are about to slip based on a set logic. It then outputs signals to operate the solenoid valves inside the hydraulic unit in order to help prevent any of the wheels from locking up.
- Electronic Brake-force Distribution system (EBD) control has been added to provide the ideal braking force for the rear wheels.

BRAKE FLUID PRESSURE CONTROL
ABS CONTROL CYCLE
This is basically the same as for the MIRAGE.

CONTROLLING VEHICLE SPEED
The ABS can operate when the vehicle speed is approximately 10 km/h (6 mph) or higher.

EBD HYDRAULIC PRESSURE CONTROL








The EBD control operates at the low slip region where the ABS does not operate.
The EBD control calculates the vehicle deceleration and the slip amount of front/rear wheels based on the wheel speed sensor signal. When the difference between the rear wheel speed and the vehicle speed exceeds the set value, the solenoid valve for the rear wheel in the hydraulic unit is operated through the pressure conditions of increase, hold and decrease to control the rear braking hydraulic pressure to the value almost near the ideal distribution curve.
When the slip ratio of each wheel increases, the control is switched to the ABS control.

INITIAL CHECK FUNCTION
The ABS-ECU uses its diagnostic function to carry out the following initial checks (which take approximately one second).
The ABS warning light relay turns on and the ABS warning light illuminates for approximately three seconds after the ignition switch is turned on, and the initial check is carried out during this time. In addition, if a problem is discovered, the ABS function is stopped.

NOTE: The warning light may remain illuminated after the ignition switch is turned on until the forward vehicle speed reaches approximately 8 km/in (5 mph). This occurs only when the ABS-ECU has stored a diagnostic trouble code related to the wheel speed sensors or the pump motor from a previous problem. The ABS warning light will remain illuminate until the point where the system is able to check that the problem corresponding to this diagnostic trouble code has returned to normal (driving check).

INITIAL CHECK OPERATION





1. When the ignition switch is turned to the ON position, power is supplied to the ABS-ECU and internal ABS-ECU diagnostic test mode is carried out.
2. Next, the ABS-ECU turns the ABS valve relay inside the ECU ON, OFF and back ON again to carry out self-diagnosis of the ABS valve relay to see if there are any problems with the relay turning off and on.
3. At the same time as the operation in 2. is carried out, the drive signals and monitoring values are compared at each solenoid valves are off. (No current is supplied to the solenoid valves during this check.)
4. When the ignition switch is turned to the START position, the power supply to the ABS-ECU is interrupted and the ABS warning light relay turns on. The ABS warning light illuminates as a result of this.
5. When the engine starts and the ignition switch returns to the ON position, power is again supplied to the ABS-ECU, so that the initial check described in 1. to 3. is carried out once more.
6. Once the initial check is completed normally, ABS operation is then possible.

CHECK DURING STARTING
When the forward vehicle speed reaches approximately 8 km/in (5 mph), the ABS-ECU carries out the following checks.

MOTOR AND SOLENOID VALVE CHECK (ONLY DURING INITIAL STARTING-OFF)
The ABS motor relay inside the ECU is turned on for approximately 0.3 seconds to check the driving of the pump motor. At the same time, each solenoid valve is energized in order for an extremely short time to check the driving of the solenoid valves.

NOTE: Initial starting-off refers to the first time the vehicle drives forward after the system is activated.

WHEEL SPEED SENSOR CHECK
The ABS-ECU checks that there are no wheels which are not outputting a wheel speed sensor signal after starting off.

CONSTANT CHECK
The ABS-ECU constantly checks the following items.

ABS-ECU
ECU diagnostic test mode is carried out.

ECU POWER SUPPLY
The ECU power supply voltage is checked whether it is within the operating range.

WHEEL SPEED SENSORS
1. The output voltages of the sensor signal wires are monitored to check that there are no abnormal output voltages (open circuits or short-circuits).
2. If the wheel speed for even a single wheel is approximately 8 km/h (5 mph) or greater, checks are carried out to see whether the wheel speeds for the other wheels are being input normally.
3. Checks are carried out to see that there are no wheels showing abnormal deceleration or no pulses during driving.
4. When the vehicle speed is approximately 20 km/h (12 mph) or more, a check is made that there are no wheel speeds being input which are abnormally higher or lower than the vehicle speed.

STOPLIGHT SWITCH
The stoplight switch is checked for open circuits and short-circuits.

PUMP MOTOR AND SOLENOID VALVES
The output signals from the ABS-ECU itself and the drive states of the pump motor and solenoid valves are checked to ensure that they are identical.

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