Circuit Operation

The Stepper Motor Cruise Control (SMCC) is a speed control system which maintains a desired vehicle speed under normal driving conditions. However, steep grades up or down may cause variations in the selected speeds. The system has the capability to cruise, coast, resume speed, accelerate, tap-up, and tap-down.

An electronic controller and electric motor are contained in the cruise control module. The controller monitors vehicle speed and operates the electric motor. In response to the controller, the motor moves a connecting strap that is attached to the cruise control cable. The cable moves the throttle linkage to vary throttle position in order to maintain the desired cruise speed. The cruise control module contains a low speed limit which will prevent system engagement below a minimum speed, approximately 40 km/h (25 mph). The module is controlled by mode control switches located on the cruise control switch. Cruise control is in the standby disabled mode until all conditions inconsistent with cruise control operation are cleared.

Ignition voltage is supplied from the CRUISE Fuse, through circuit 341 to terminal F of the cruise control module. The cruise control module receives ground at terminal E, through circuit 1750, and from G201. When the slider switch is moved to the ON position, battery voltage is applied through circuit 397 to terminal A of the cruise control module connector. If the brake pedal is not depressed, battery voltage is present from circuit 341 through the cruise control release switch and circuit 86 to the cruise control module terminal D. If the brake pedal is depressed, battery voltage is supplied from the STOP LAMP Fuse, through circuit 140, the stop lamp switch and circuit 17 to the cruise control module terminal 0. Terminal 0 must see current flow through the Center High-Mounted Stop Lamp (CHMSL) bulbs for cruise to operate (disable) properly. When the slider switch is moved to the R/A position, battery voltage is applied through circuit 87 to terminal C of the cruise control module. With the Set switch depressed, battery voltage is present through circuit 84to the cruise control module terminal B. The cruise control module terminal K is the speed signal terminal through circuit 817. In operation, the voltage will oscillate between a high of 4 to 5 volts and a low of near ground. The cruise control module terminal J is used to signal the Powertrain Control Module (PCM) when cruise control is engaged through circuit 85. The PCM will then determine the correct shift pattern for the transmission. The cruise control module terminal H is used by the PCM through circuit 83, to inhibit cruise control when conditions inconsistent with cruise operation are present. These are the cruise control inhibit criteria.

The PCM will inhibit cruise control:
^ When vehicle speed is less than 40 km/h (25 mph).
^ When PARK, REVERSE, NEUTRAL, or 1st gear is indicated by the transaxle range switch.
^ When an over/under battery voltage condition exists.
^ With low engine RPM.
^ With high engine RPM (fuel cut-off).