Cruise Control: Description and 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 under the righthand side of the air cleaner.

The controls are located on the steering wheel. The controls consist of a SET/COAST, RESUME/ACCEL and ON and OFF buttons. This system is designed to operate at speed exceeding 35 mph.

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

To deactivate system push the OFF button or lightly tap on brake pedal.

When the operator turns the system ON, the Powertrain Control Module (PCM) measures the change voltage on circuit V37 to determine operator request.

The PCM then grounds the V38 circuit. This causes the vehicle speed control relay to energize connecting the G5 and V32 circuits.

When the system is turned ON, the vehicle is moving forward, vehicle speed is above 35 mph, and the SET switch is pressed, the Powertrain Control Module (PCM) looks at the vehicle speed. The vehicle speed input is provided from the Transmission Control Module (TCM) to the PCM on circuit G7.

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 33 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 53 of the PCM.

Grounding for the vehicle speed control servo is done on the Z1 circuit. Circuit Z1 terminates at the left front frame rail.

If the stop lamp switch is pressed while the vehicle speed control is engaged, the power supply path from the switch to the servo is terminated and the servo is vented causing the vehicle speed control to disengage.

If the vehicle speed control switch is turned OFF, the PCM terminates the ground for circuit V38. This causes the vehicle speed control relay to switch from its powered position to its normal position.