DESCRIPTION
By using the auto-cruise control, the driver can drive at the desired speed in a range or approximately 40-200 km/h (25-124 mph) without depressing the accelerator pedal. (Scheme 1)
Scheme 1
Scheme 2
Introduction To Auto-Cruise Control System Diagnosis
The auto-cruise control system allows driving without stepping on the accelerator pedal by setting a random speed between 40 km/h (25 mph) and 200 km/h (124 mph).
Problems in this system can be investigated by the following methods
Auto-Cruise Control System Diagnostic Trouble Codes
The auto-cruise control system consists of the auto-cruise control-ECU, control switches, sensors, and vacuum pump.
The control switches and sensors monitor the state of the vehicle.
Based on the input signals from those switches and sensors, the auto-cruise control-ECU activates the vacuum pump.
If the auto-cruise control-ECU detects a problem on any of those components, the ECU estimates where the problem may be occurring, and will output a diagnostic code.
Diagnostic trouble codes cover the throttle position sensor, auto-cruise control switch, vehicle speed sensor, auto-cruise control-ECU and vacuum pump.
Circuit Operation
This circuit activates the vacuum pump used to accelerate/decelerate, set, and cancel the vehicle speed.
The auto-cruise control-ECU controls the control valve, release valve, and motor by turning the transistor in the ECU on and off.
This circuit checks the operation of the vehicle speed sensor. When the vehicle moves forward and reverses, the sensor turns ON and OFF repeatedly.
This circuit checks the vehicle speed signal. When the vehicle moves forward and reverses, the sensor turns ON and OFF repeatedly.
This circuit supplies the power to the vacuum pump. The battery positive voltage is supplied to the auto-cruise control vacuum pump by turning on the transistor at terminal No. 16 of the auto-cruise control-ECU. The conditions for turning on the transistor at terminal No. 16 of the auto-cruise control-ECU are as follows
- Ignition switch ON.
- Auto-cruise control main switch ON.
- Stoplight switch ON.
This circuit judges the signals of each switch (OFF, SET, RESUME, CANCEL and MAIN) of the auto-cruise control switch. The auto-cruise control-ECU detects the state of the auto-cruise control switch by sensing the voltages.
- When all switches are OFF, the ECU detects 3.5-5.0 volts.
- When the SET switch is ON, the ECU detects 0.4-2.3 volts.
- When the CANCEL switch is ON, the ECU detects 0.4 volts or less.
- When the main switch is ON, the ECU detects 7.0 volts.
The throttle position sensor signal and idle position signal are sent to the auto-cruise control-ECU throughout this circuit.
The throttle position sensor sends a voltage signal to terminal No. 1 of the auto-cruise control-ECU. The voltage depends on throttle opening angle.
The auto-cruise control-ECU receives an idle position signal from the ECM at terminal No. 2. The signal is OFF when the accelerator pedal is depressed, and ON when the accelerator pedal is released.
The throttle position sensor signal is sent to the auto-cruise control-ECU through this circuit. The auto-cruise control-ECU receives a signal from the throttle position sensor at terminal No. 1. The signal is OFF when the accelerator pedal is depressed, and ON when the accelerator pedal is released. The throttle position sensor sends a voltage signal to terminal No. 1 of the auto-cruise control-ECU. The voltage depends on throttle opening angle.
Power of the auto-cruise control-ECU is transmitted from the ignition switch (IG1) to the auto-cruise control-ECU through multi-purpose fuse 13 in the junction block.
Technical Description (Comment)
The cause is probably a malfunction of the auto-cruise control-ECU power supply circuit or the auto-cruise control-ECU ground circuit.
This is the stoplight switch input signal circuit. The signal is sent to the stoplight switch from multipurpose fuse No. 3, and is then sent to the auto-cruise control-ECU.
The cause is probably a malfunction of the stoplight switch circuit.
This circuit indicated the operation status of the clutch pedal position switch. When the clutch pedal position switch is ON (clutch pedal is depressed), the voltage of auto-cruise control-ECU terminal No. 13 will indicate 0 volt.
The cause is probably a malfunction of the clutch pedal position switch circuit.
This circuit transmits the "N" or "P" position signal of the Park/Neutral position switch to the auto-cruise control-ECU. When the Park/Neutral position switch is at the "N" or "P" position, auto-cruise control-ECU terminal No. 13 will receive 0 volts.
The cause is probably an open-circuit in the output signal circuit in "N" range.
Technical Description
The cause is probably an open-circuit in the output in the circuit inside the "CANCEL" switch.
The fail-safe function is probably cancelling auto-cruise control. In this case, scan tool MB991502 can be used to check the trouble symptoms in each system by checking the diagnostic trouble codes. The scan tool can also be used to check if the circuits of each input switch are normal or not by checking the input switch codes.
The cause is probably the malfunction of the vehicle speed sensor or incorrect vacuum in the auto-cruise control vacuum pump or actuator.
The cause is probably the malfunction of the output shaft speed sensor or PCM or incorrect vacuum in the auto-cruise control vacuum pump or actuator.
The power for the auto-cruise indicator in the combination meter is supplied from the ignition switch (IG1). When the auto-cruise control system is operating, the transistor inside the auto-cruise control-ECU illuminates the auto-cruise indicator through ECU terminal No. 15.
The cause is probably the malfunction of the indicator bulb or the malfunction of the connector or harness.