DESCRIPTION & OPERATION
| WARNING | Because of Supplemental Inflatable Restraint (SIR) system, before any repairs are performed, disconnect and shield battery ground. Because system has ability to retain voltage, remove SIR fuse and disconnect Yellow SIR connector at base of steering column. Wait 15 minutes before beginning service. All connectors used on SIR system use Connector Position Assurance (CPA) clips to ensure connector retention. Even if system is disconnected, use caution when working near steering column. |
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See the COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION section before disconnecting battery. |
Cruise control system operates a mechanical linkage to throttle by means of a vacuum servo. Based on various inputs, Powertrain Control Module (PCM) controls solenoid valves at servo assembly. Valves control vacuum supply to servo diaphragm. Servo sets position of throttle to maintain cruise speed. Cruise will not engage at speeds of less than 25 MPH. Any of the following conditions will prevent system operation
- Cruise control switch is turned off
- Brakes are applied
- Transaxle is shifted into Park, Neutral, Reverse or L1 (low gear)
- SET and R/A switches are pressed at the same time
- PCM diagnostic code is set
- Engine speed is greater than 5400 RPM or less than 500 RPM
- Rate of acceleration or deceleration exceeds calibrated limits.
CRUISE CONTROL SWITCH
Switch is located on end of multifunction lever (turn signal lever). Switch consists of a SET button, and a sliding switch with OFF, ON and R/A positions
OFF
System disengages when switch is turned off.
System is ready to be set when switch is turned on.
SET (Set/Coast)
Spring-loaded SET button engages cruise. During engagement, if SET button is pressed and held, vehicle decelerates (cruise disengages) until button is released. When button is released, cruise engages and maintains vehicle speed at new speed. Also, by quickly pressing and releasing (tapping) this button, the set speed is "tapped" down in one MPH increments.
R/A (Resume/Accelerate)
Spring-loaded R/A switch will not initially set cruise speed, but when cruise has been disengaged by braking, momentarily sliding this switch to R/A position will cause cruise to resume previously set speed. This is the resume function. Accelerate function occurs when R/A switch is held in position for more than one second. This causes the vehicle to accelerate until switch is released. When released, system maintains new set speed. Also, by quickly pressing and releasing (tapping) this button, the set speed is "tapped" up in 1 MPH increments.
POWERTRAIN CONTROL MODULE (PCM)
PCM is located behind right side of instrument panel, next to relay center. PCM receives inputs from the cruise control switch, throttle position sensor, brake release switches, vehicle speed sensor and cruise control servo position sensor. Based on input from these sensors, PCM controls vent and vacuum solenoid valves in servo.
CRUISE CONTROL SERVO
Servo consists of a vacuum-actuated diaphragm, a normally open vent solenoid valve (vents diaphragm chamber to atmosphere), a normally closed vacuum solenoid valve (connects diaphragm chamber to vacuum source) and a variable inductance position sensor. During engagement, the servo positions the throttle in response to signals from PCM as follows
Steady Cruise
PCM keeps both valves (vacuum and vent) closed, trapping vacuum in servo diaphragm chamber.
Vehicle Losing Speed
PCM opens vacuum valve to vacuum source. This increases vacuum level in chamber, opening throttle further. Vent valve remains closed.
Vehicle Gaining Speed
PCM opens vent valve to atmosphere, reducing vacuum level in chamber and reducing throttle angle. Vacuum valve remains closed.
VACUUM SUPPLY
Engine manifold supplies vacuum for servo diaphragm. Vacuum tank stores vacuum for reserve supply. Vacuum check valve, located between engine vacuum harness and cruise control vacuum harness, prevents vacuum from escaping through engine vacuum harness. If check valve is defective, vehicle may be sluggish or cruise control operation may be erratic.
VEHICLE SPEED SENSOR (VSS)
VSS is located on right transaxle extension case, near axle shaft. This Permanent Magnet (PM) generator, driven by transmission, generates vehicle speed information in form of a low-voltage AC signal. Frequency is proportional to vehicle speed. PCM uses signal as a comparison to determine if vehicle speed is equal to cruise set speed.
BRAKE RELEASE SWITCHES
System uses a vacuum release switch and one or more electrical release switches to vent servo vacuum to atmosphere, allowing throttle to quickly close. Switches are mounted on brake pedal bracket. When brake pedal is pressed
- Vacuum release switch directly vents servo vacuum
- PCM receives signal from electrical release switch, then opens vent valve.
CRUISE CONTROL INDICATOR LIGHT
CRUISE control indicator light (if equipped) comes on when cruise control is engaged.
CRUISE CONTROL CABLE
Note. DO NOT stretch cable assembly to secure a particular tab hole. If cable is stretched, engine will not return to idle.
Remove retainer from servo blade (metal tab where cable is connected to servo). Disconnect cable from servo blade. Ensure throttle is fully closed. Connect cable to servo blade so minimum slack exists in cable. Cable must NOT be taught. Install retainer at servo blade. Retainer must be installed with tang secured over cable stud head.
BRAKE RELEASE SWITCH
Fully press and hold brake pedal. Press switch fully forward until firmly seated into mounting bracket. Pull brake pedal rearward until clicks are no longer heard. This moves switch rearward in retainer, providing adjustment. When correctly adjusted, only the notch at end of switch plunger should be visible. If rest of plunger is visible or if notch is not visible, readjust switch.
See code charts in TESTS W/CODES article in the ENGINE PERFORMANCE section.
TESTS W/CODES - "C" Body
TESTS W/CODES - "H" Body
There is no available component testing from the manufacturer. The cruise control system is controlled by the Powertrain Control Module (PCM). For testing see code charts in TESTS W/CODES article in the ENGINE PERFORMANCE section.
TESTS W/CODES - "C" Body
TESTS W/CODES - "H" Body
| Application (Terminals) | Ohms |
|---|---|
| Vacuum Valve (E & C) | 30-55 |
| Vacuum Valve (A & C) | 30-55 |
CRUISE CONTROL SERVO RESISTANCE
TROUBLE SHOOTING
Check fuses. Check for disconnected or damaged wiring. Check for pinched, cracked, plugged or disconnected vacuum hoses. Check for binding or misadjusted cruise control cable. Check operation of brake release switches.
REMOVAL & INSTALLATION
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See the COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION section before disconnecting battery. |
Removal
Disconnect negative battery cable. Remove sound insulator under left side of instrument panel. Disconnect electrical connectors and vacuum hoses from switch. Remove switch from retainer. Remove retainer from brake pedal mounting bracket.
Installation
To install, reverse removal procedure. Adjust switch. See BRAKE RELEASE SWITCH under ADJUSTMENTS.
Remove retainer from servo blade (metal tab where cable is connected to servo). Disconnect cable end from servo blade. Disconnect cable end from throttle lever. Release locking tangs and disconnect cable housing from servo bracket and engine bracket. Remove cable.
To install, reverse removal procedure. Before connecting cable end to servo blade, ensure throttle is fully closed. Connect cable to servo blade so minimum slack exists in cable. Cable must NOT be taught. Install retainer at servo blade. Retainer must be installed with tang secured over cable stud head.
Remove cable retainer from servo blade (metal tab where cable connects to servo). Disconnect vacuum hoses and electrical connectors from servo. Remove servo and mounting bracket as an assembly. Remove servo from mounting bracket. To install, reverse removal procedure.
Set multifunction lever in middle (centered) position. Remove access cover from steering column. Disconnect cruise control switch electrical connector. Pull multifunction lever toward driver's door to release. Remove multifunction lever. To install, reverse removal procedure.
Disconnect negative battery cable. Remove right sound insulator under instrument panel. Disconnect PCM electrical connector. Remove PCM mounting brackets. Remove PCM. If replacing PCM, remove MEM-CAL access cover and transfer MEM-CAL to new PCM. To install, reverse removal procedure.
Raise and support vehicle. Disconnect VSS electrical connector. Remove VSS bolt. Remove VSS. Remove "O" ring from VSS. To install, reverse removal procedure.
See also:
• COMPUTER RELEARN PROCEDURES
• TESTS W/CODES