Automatic Slip Reduction (ASR)

ELECTRONIC CONTROL UNIT (ASR ECU)

The ASR ECU has two functions; deciding when traction control mode is needed and operating the kickdown wire motor.
The ASR ECU is an addition to the ETS ECU. Both ECUs can be found below the driver's seat fixed to a mounting bracket. Several wires from the ASR ECU are connected to the ETS ECU, since the two units share many of the same signals.

Fig. 3 Kickdown Wire & Motor Assembly:

KICKDOWN WIRE SETTING MOTOR

The kickdown wire (KDW) motor that controls the kickdown cable is located on a separate bracket on the engine frame adjacent to the steering rack, Fig. 3.
The main purpose of the motor is to replace the lever on the conventional throttle valve housing, since the ETS throttle valve has no lever. Position of the KDW is proportional at all times to the actual position of the accelerator. The KDW motor includes a potentiometer which informs the ASR ECU of KDW position at all times.

Limp-Home Mode - Kickdown Wire

If a fault occurs in the ASR system, or in the ETS system which is critical to the operation of Traction Control, the system will revert to the limp-home mode.
In the limp-home mode, the kickdown wire is set to a fixed position of approximately 40 percent of full travel. At the same time, engine torque is limited to a maximum of 85 percent of normal through control of the throttle valve opening position.
This torque limitation combined with the fixed position of the kickdown wire help prevent any transmission slippage.


PEDAL & THROTTLE POTENTIOMETERS

The ASR ECU constantly compares the signal at pin 1 (pedal potentiometer position) with the signal at pin 3 (throttle potentiometer position). If there is an abnormal deviation between the two signals, the system will revert to the limp-home position.

WHEEL SPEED SIGNALS

The ASR ECU receives wheel speed information from the Antilock Brake System Electronic Control Unit (ABS ECU). The ABS ECU receives and AC. voltage from each wheel speed sensor, and converts the AC. voltage to a digital square wave. As the speed of the wheel increases, the frequency of the AC. voltage increases, so the ABS ECU increases the frequency of the digital square wave. Test pulses are generated by the ABS ECU so that the ASR ECU can check for continuity of the signal wires even when the car is stationary.
If there is a deviation in the speed of either front wheel when compared with the reference speed (average rear wheel speed), the ASR ECU sends a signal to the ETS ECU to decrease the throttle opening to stop the wheel spin.

GEAR SELECTOR SIGNAL

The ASR ECU receives information from the gear selector switch regarding gear selector position. When the gear selector is in Park or Neutral there is no signal (zero volts). When the gear selector is placed in any driving position, the ASR ECU receives a 12 volt signal. The ASR ECU then sends a signal to the ETS ECU for idle compensation.