Active Skid Control System (Asc) - Lancer Evolution: Overview Mitsubishi Lancer X

GENERAL INFORMATION

Active skid control (ASC) has been equipped as a standard.

1. ASC has been added to the transaxle < twin clutch sportronic shift transmission (TC-SST) *1 > control and AWD < super all wheel control (S-AWC) *2 > control, and the controls are integrated to improve the vehicle stability.
2. The ASC system integrates the traction control (TCL) function and skid control function.
3. When the TCL function detects the slip of driving wheel (for example, during startup on slippery road), it automatically applies the braking force to the slipping driving wheel. At the same time, TCL reduces the engine output and prevents the wheel spin when it determines that the engine torque is too high for the road surface friction coefficient.
4. When the skid control function determines that the vehicle behavior is in a critical state, it reduces the engine output and applies brake force to four wheels independently to control the vehicle behavior, avoiding the critical state.
5. Brake performance at ASC system failure is ensured by the fail-safe function, and at the same time, the serviceability during service is improved.

Note. *1 : For the details on twin clutch sportronic shift transmission (TC-SST), refer to technical information manual. *2 : For the details on super all wheel control (S-AWC), refer to technical information manual. The active skid control (ASC) has the traction control function and the skid control function. By the integrated control with the anti-lock brake system, the system stabilizes the vehicle attitude and, at the same time, secures the driving force.

Scheme 2

INTRODUCTION TO ASC DIAGNOSIS

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

Some operational characteristics may seem to be malfunctions, but they are simply signs of normal ASC operation. When diagnosing the ASC system, keep these operational characteristics in mind. Inform the owner of the kind of performance characteristics to expect from an ASC-equipped vehicle.

CIRCUIT OPERATION

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. Each wheel speed detecting section is a kind of a pulse generator. It consists of the encoder (plate on which the north and south pole of magnet are arranged alternately) for detecting the wheel speed, which rotates at the same speed of the wheels, and the wheel speed sensor. This detecting section outputs the frequency pulse signals in proportion to the wheel speed.
2. The pulse signals generated by the wheel speed detecting section are sent to ASC-ECU. ASC-ECU uses the frequency of the pulse signals to determine the wheel speed.

1. ASC-ECU contains the power supply circuit (terminal No. 32) for the solenoid valve. The solenoid valve is energized by the valve relay, which is incorporated in ASC-ECU.
2. The valve relay in ASC-ECU is energized at all times, and the solenoid valve is always energized while the system is in operation unless the initial check is in progress when the ignition switch is turned ON, or unless the periodical system check is in progress.
3. ASC-ECU activates the solenoid valve by turning on its driving transistor.

1. ASC-ECU contains the power supply circuit (terminal No. 32) for the solenoid valve. The solenoid valve is energized by the valve relay, which is incorporated in ASC-ECU.
2. The valve relay in ASC-ECU is energized at all times, and the solenoid valve is always energized while the system is in operation unless the initial check is in progress when the ignition switch is turned ON, or unless the periodical system check is in progress.

1. ASC-ECU contains the power supply circuit (terminal No. 1) for the motor. The pump motor is energized by the pump motor switch, which is incorporated in ASC-ECU.
2. The pump motor switch in ASC-ECU is turned off at all times unless during the motor solenoid valve check performed when the vehicle is started.
3. ASC-ECU activates the pump motor by turning on the ECU built-in pump motor switch.

1. ASC-ECU contains the power supply circuit (terminal No. 1) for the motor. The pump motor is energized by the pump motor switch, which is incorporated in ASC-ECU.
2. The pump motor switch in ASC-ECU is turned off at all times unless during the motor solenoid valve check performed when the vehicle is started.
3. ASC-ECU activates the pump motor by turning on the ECU built-in pump motor switch.

The pressure sensor is incorporated in the hydraulic unit. When the brake pedal is depressed, the pressure sensor detects the brake pressure applied from the master cylinder, converts this pressure into the voltage signal, and then outputs the signal.

The pressure sensor is incorporated in the hydraulic unit. When the brake pedal is depressed, the pressure sensor detects the brake pressure applied from the master cylinder, converts this pressure into the voltage signal, and then outputs the signal.

The wheel cylinder pressure sensor is integrated into the hydraulic unit. It converts the signal of brake fluid pressure in wheel cylinder of each wheel to the voltage value, then outputs the value to ASC-ECU.

1. The wheel cylinder pressure sensor is integrated into the hydraulic unit. It converts the signal of brake fluid pressure in wheel cylinder of each wheel to the voltage value, then outputs the value to ASC-ECU.
2. The wheel cylinder pressure sensor contains the following two signal output sections: Fluid pressure signal output section and fluid pressure and temperature signal output section.

ETACS-ECU sends the ON signal generated when the brake pedal is depressed and OFF signal generated when the pedal is released to ASC-ECU via CAN bus lines.

DTC C123B: Prolonged operation of ASC

ASC-ECU controls ASC by calculating the data sent from the wheel speed sensor, steering wheel sensor, and G and yaw rate sensor.

ASC-ECU controls ASC by calculating the data sent from the wheel speed sensor, steering wheel sensor, and G and yaw rate sensor.

1. ASC-ECU contains the power supply circuit (terminal No. 32) for the solenoid valve. The solenoid valve is energized by the valve relay, which is incorporated in ASC-ECU.
2. ASC-ECU contains the power supply circuit (terminal No. 2) for ASC-ECU, and the power is supplied from the fusible link No. 34 through the multi-purpose fuse No. 17.
3. The valve relay in ASC-ECU is energized at all times, and the solenoid valve is always energized while the system is in operation unless the initial check is in progress when the ignition switch is turned ON, or unless the periodical system check is in progress.

ASC-ECU sends the signal to the engine control module as necessary to decrease the engine output for ASC system operation.

ASC-ECU receives signals necessary for the operations of ABS, skid control, and TCL from the engine control module, transaxle assembly (with built-in ECU) < TC-SST >, S-AWC-ECU, ETACS-ECU, and the steering wheel sensor via the CAN bus lines.

ASC-ECU receives vehicle information from the engine control module and stores it.

ASC-ECU receives the vehicle information stored in ETACS-ECU via CAN bus lines.

1. ASC-ECU supplies power to the G and yaw rate sensor at the terminal No. 1.
2. The G and yaw rate sensor outputs the signal to ASC-ECU via the special CAN bus lines.

1. ASC-ECU supplies power to the G and yaw rate sensor at the terminal No. 1.
2. The G and yaw rate sensor outputs the signal to ASC-ECU via the special CAN bus lines.

1. ASC-ECU supplies power to the G and yaw rate sensor at the terminal No. 1.
2. The G and yaw rate sensor outputs the signal to ASC-ECU via the special CAN bus lines.

1. ASC-ECU supplies power to the G and yaw rate sensor at the terminal No. 1.
2. The G and yaw rate sensor outputs the signal to ASC-ECU via the special CAN bus lines.

When the brake pedal is depressed, the master cylinder pressure sensor integrated in the hydraulic unit detects the brake fluid pressure applied from the master cylinder. At the same time, it converts the pressure value into voltage signal, and outputs the signal.

1. ASC-ECU supplies power to the G and yaw rate sensor at the terminal No. 1.
2. The G and yaw rate sensor outputs the signal to ASC-ECU via the special CAN bus lines.

ASC-ECU stores the calibrated value of the G and yaw rate sensor, steering wheel sensor, and master cylinder pressure sensor.

Steering wheel sensor outputs the signal to ASC-ECU via CAN bus lines.

Steering wheel sensor stores the neutral position learned using scan tool MB991958. When the neutral position has not been learned, the steering wheel sensor outputs the signal indicating that the learning has not been performed.

Steering wheel sensor sends its status signal to ASC-ECU.

The ASC-ECU stores diagnostic trouble codes and failure information in the EEPROM*.

Note. *:EEPROM (Electrical Erasable and Programmable ROM)

ASC-ECU stores the correction values of cut valve and inlet valve in the EEPROM.

ASC-ECU communicates with the engine control module, TC-SST-ECU, steering wheel sensor, ETACS-ECU, and AWC-ECU via the CAN bus lines.

The G and yaw rate sensor outputs the signal to ASC-ECU and S-AWC-ECU via the special CAN bus lines (Local CAN).

Engine-related signals are sent or received to and from between ASC-ECU and engine ECU via CAN bus lines.

The steering wheel sensor outputs the steering wheel status to ASC-ECU via the CAN bus lines.

S-AWC-ECU outputs the signal to ASC-ECU via the special CAN bus lines (Local CAN).

The G and yaw rate sensor outputs the signal to ASC-ECU and S-AWC-ECU via the special CAN bus lines.

ASC-ECU receives the vehicle information stored in the ETACS-ECU via CAN bus lines.

ASC-ECU receives the vehicle information stored in the ETACS-ECU via CAN bus lines.

TECHNICAL DESCRIPTION (COMMENT)

When the scan tool MB991958 cannot communicate with the ABS/ASC system, there may be a malfunction to the CAN bus lines, ASC-ECU power supply circuit system, ground, or ASC-ECU.

1. When the parking brake switch is turned ON, the combination meter terminal No. 4 is grounded, and then the brake warning light is illuminated.
2. When the brake fluid level drop is detected, the brake fluid level switch is turned from ON to OFF. ETACS-ECU monitors the brake fluid level switch, and gives an instruction via the CAN bus line to the combination meter to illuminate the brake warning light.

SYSTEM OPERATION

1. ASC-ECU sends the illumination signal of ABS warning light to the combination meter through ETACS-ECU via CAN communication.
2. When the ignition switch is turned ON, ASC-ECU illuminates the ABS warning light via ETACS-ECU for approximately 3 seconds for the purpose of bulb check.

In the case of this trouble symptom, there may be a malfunction to the CAN bus line, ETACS-ECU, combination meter, or ASC-ECU.

1. ASC-ECU sends the illumination request signal of the brake warning light to the combination meter through ETACS-ECU via CAN communication.
2. When the ignition switch is turned ON, ASC-ECU illuminates the brake warning light via ETACS-ECU for approximately 3 seconds for the purpose of bulb check.

In the case of this trouble symptom, there may be a malfunction to the CAN bus line, ETACS-ECU, combination meter, or ASC-ECU.

1. ASC-ECU sends the illumination signal of ABS warning light to the combination meter through ETACS-ECU via CAN communication.
2. When the ignition switch is turned ON, ASC-ECU illuminates the ABS warning light via ETACS-ECU for approximately 3 seconds for the purpose of bulb check.

In the case of this trouble symptom, there may be a malfunction to the CAN bus line, ETACS-ECU, combination meter, or ASC-ECU.

ASC-ECU sends the illumination request signal of ASC warning display to the combination meter through ETACS-ECU via CAN communication.

In the case of this trouble symptom, there may be a malfunction to the CAN bus line, ETACS-ECU, combination meter, or ASC-ECU.

1. ASC-ECU sends the illumination request signal of ASC OFF display to the combination meter through ETACS-ECU via CAN communication.
2. By the operation of ASC OFF switch, the ASC OFF display illuminates when the ASC function is stopped.
3. When the ASC OFF switch is pressed shortly, the ASC system is turned OFF.

In the case of this trouble symptom, there may be a short circuit to the ASC OFF switch circuit.

1. The ETACS-ECU terminal No. 15 is grounded when the ASC OFF switch is pressed. The ON/OFF status of ASC OFF switch is sent from ETACS-ECU to ASC-ECU via CAN bus line.
2. When the ASC OFF switch is pressed shortly, the ASC system is turned OFF.
3. When the ASC OFF switch is pressed and held for 15 seconds or more, the ASC OFF indicator light is turned off, and the ASC system is turned ON.

In the case of this trouble symptom, there may be an open circuit to the ASC OFF switch circuit.

Inspection Procedure 9: Abnormality in brake operation

Although it is difficult to determine the trouble cause since it depends on the running status and road surface condition, a malfunction of hydraulic circuit may be present if no diagnostic trouble code is detected.

In case of this trouble symptom, the operation of skid control/TCL system may be disabled. In this case, a diagnostic trouble code may be set by the skid control/TCL system using the scan tool.

1. ASC-ECU contains the power supply circuit (terminal No. 32) for the solenoid valve. The solenoid valve is energized by the valve relay, which is incorporated in ASC-ECU.
2. ASC-ECU contains the power supply circuit (terminal No. 1) for the pump motor. The pump motor is energized by the motor relay, which is incorporated in ASC-ECU.
3. ASC-ECU contains the power supply circuit (terminal No. 2) for ASC-ECU, and the power is supplied from the fusible link No. 34 through the multi-purpose fuse No. 17.
4. If a malfunction occurs in the ASC-ECU power supply, the communication with scan tool becomes unavailable.