Cruise Control: Description and Operation

OPERATION
This Speed Control System is electrically controlled and vacuum operated. The electronic control is integrated into the Powertrain Control Module (PCM). The PCM is located on the left fender shield.

The controls are located on the steering wheel. The controls consist of two switch pods. The ON and OFF buttons are located on the upper left side of the air bag module. The RESUME/ACCEL, SET/COAST and CANCEL buttons are located on the upper right side of the air bag module. This system is designed to operate at speeds exceeding 30 MPH.

To activate the system, push the ON button. When the desired speed is obtained, push the SET/COAST button to engage the system.

To deactivate the system, push the OFF button, lightly tap on brake pedal, or push the CANCEL button, which will disengage the speed control without erasing the speed set in memory.

CIRCUIT OPERATION
The vehicle speed control system is powered by the Powertrain Control Module (PCM). The vehicle speed control switches, located in the steering wheel, use resistors internal to the switch to send a signal to the PCM indicating what the operator is requesting. The V37 circuit, from cavity 41 of the PCM supplies power for the switch. Circuit Z2 is the ground for the switch. The Z2 circuit terminates at the instrument panel left side cowl.

The V37 and Z2 circuits are spliced internal to the clockspring to provide power and ground for the two switches.

When the system is turned ON, the vehicle is moving forward, vehicle speed is above 35 mph (50 kph), and the SET switch is pressed, the PCM looks at the vehicle speed.

With this information, the PCM sends a signal to the vehicle speed control servo, on the V36 circuit, and the servo applies vacuum to hold the desired speed. Circuit V36 connects to cavity 78 of the PCM.

When the operator selects the COAST feature in the system, the PCM measures the resistance on the V37 circuit and uses this information to apply voltage on the V35 circuit, which is the vent side of the vehicle speed control servo. Circuit V35 connects to cavity 80 of the PCM.

Grounding for the vehicle speed control servo is supplied on the Z2 circuit. Circuit Z2 terminates at the left strut tower. An additional input to the servo is provided by the stop lamp switch on the V30 circuit. When the operator presses on the brakes the ground path for the V30 circuit is broken. This break in the ground path causes the vehicle speed control servo to vent and disengage the system.

Circuits V32 and K29 are used as inputs to the PCM to indicate when the operator is applying the brakes, as vehicle speed control is canceled when this happens. Circuit V32 connects to cavity 5 of the PCM. Circuit K29 connects to cavity 62 of the PCM.