Cruise Control Description
The Cruise Control system operates a mechanical linkage to the throttle by means of a Vacuum Motor. This is a diaphragm moved by a vacuum applied to one side. A solenoid operated valve connects the Vacuum Motor to engine vacuum. Another Solenoid Valve vents the vacuum to reduce suction. The Powertrain Control Module (PCM) controls the Vacuum Motor and the throttle by pulsing these solenoid valves on and off.The inputs to the PCM for control of the Cruise Control system are:
^ Cruise ON from the Cruise Control Switch on the Multi-Function Lever.
^ Brake Inputs from the Brake Switch and the VCC Brake Switch. Both Brake Switch circuits must be functioning properly or the PCM will disable cruise.
^ Engine RPM from the distributor to provide smooth acceleration.
^ Vehicle Speed from the Vehicle Speed Sensor to determine if the actual vehicle speed is different from the cruise set speed.
^ Servo Position from the Cruise Control Servo. The Servo Position Sensor in the Cruise Control Servo senses the position and motion of the Vacuum Motor. The PCM uses this information to provide smooth acceleration when in the cruise mode.
^ Set/Coast from the Set/Coast Switch by applying battery voltage to PCM terminal 1D3 when operated.
^ Resume/Accel from the Resume/Accel Switch by applying battery voltage to PCM terminal 1C3 when operated.
^ Throttle Position from the Throttle Position Sensor (TPS).
^ Park Neutral from the Transaxle Position Switch.
There is also a vacuum shutdown of the Cruise Control Servo. The Cruise Control Vacuum Release Valve, on the brake lever support, vents all vacuum from the Vacuum Motor whenever the brake pedal is depressed.
Two outputs at PCM terminals 3F3 and 3F2 operate the Vacuum and Vent Valves. These valves move the throttle through the Vacuum Motor. The PCM pulses these valves on and off as necessary to maintain the proper vehicle speed.
The CRUISE CONTROL Indicator in the IPC is controlled through the serial data line (800). The PCM sends out the cruise mode status.