Cruise Control: Description and Operation

How the Circuit Works
The vehicle does not use a throttle cable or cruise control actuator to maintain the vehicle speed during the cruise control mode. A throttle actuator control motor, located on the side of the throttle housing, is used to open and close the throttle plate for routine driving and cruise conditions.

Power Supply
Battery voltage is supplied at all times through fuse 21 (in the under-hood fuse/relay box) to the ETCS control relay contacts, through fuse 19 (in the under-hood fuse/relay box) to the PGM-FI main relay 1, and through fuse 12 (in the under-hood fuse/relay box) to the MICU and brake pedal position switch.

With the ignition ON (II) or START (III), battery voltage is supplied through fuse 3 (in the under-dash fuse/relay box) to the brake pedal position switch and then to the PCM and through fuse 10 (in the under-dash fuse/relay box) to the gauge control module and then to the main switch of the cruise control combination switch.

System Description
When the main switch is pressed, a battery voltage input is removed from the gauge control module, and the cruise control main switch indicator LED illuminates. With the shift lever in D or S, a path to ground is provided for the drive input to the PCM. The PCM detects that the shift lever is in D or S through this input, which enables the cruise control.

When the set switch is pressed, a voltage signal is sent to the gauge control module. The gauge control module grounds the cruise control indicator LED, illuminating it. The gauge control module communicates the set signal via multiplex communication lines to the PCM. Using the vehicle speed input obtained from the output shaft (countershaft) speed sensor, the PCM sends signals to, and receives signals from, the TP sensor/throttle actuator, which opens and closes the throttle to maintain the set speed.

When the brake pedal is pressed, a battery voltage input is sent to the PCM through fuse 12 (in the under-hood fuse/relay box) and the battery voltage input through fuse 3 (in the under-dash fuse/relay box) is removed. The PCM communicates the brake pedal pressed information via multiplex communication lines to the gauge control module, which removes ground from the cruise control indicator LED, turning it off. The information is also used by the PCM to remove the cruise control system's control of the throttle.

When the resume switch is pressed, a voltage signal is sent to the gauge control module. The gauge control module grounds the cruise control indicator LED, illuminating it. The gauge control module communicates the resume signal via multiplex communication lines to the PCM. Using the vehicle speed input obtained from the output shaft (countershaft) speed sensor, the PCM sends signals to, and receives signals from, the TP sensor/throttle actuator, which opens and closes the throttle to resume and maintains the previously set speed.

When the cancel switch is pressed, two voltage signals are sent to the gauge control module. The gauge control module removes ground from the cruise control indicator LED, turning it off. The gauge control module communicates the cancel signal via multiplex communication lines to the PCM. The information is used by the PCM to remove the cruise control system's control of the throttle.