Buick Regal 1997-2000

System Operation

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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 combined 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 25 mph. The module is controlled by mode control switches. Cruise Control is in a "Standby Disabled" mode until all conditions inconsistent with cruise control operation are cleared.

The cruise control inhibit criteria where the PCM will "inhibit" cruise control are:



When the vehicle speed is less than 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).
 

As with most of the computer-controlled systems on these vehicles, troubleshooting requires a qualified technician using a scan tool to extract Diagnostic Trouble Codes (DTCs) and to input test commands to the system. There are, however, some basic checks that can be made.



Note the cruise control inhibit criteria listed above. Verify that a cruise control complaint really exists, and that the system is not being asked to operate at a time when the parameters for cruise control "enable" are not being met.
 
Check that the cruise control module linkage is connected and moving freely.
 
Check the stoplamp switch for proper adjustment/alignment. More information on the stoplamp switch is available in Section 9.
 
Make sure that the center high mounted stoplamp is working. If this lamp is inoperative, the cruise control module will be disabled.
 
Check for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity/voltage check with a system disconnected. These circuits may be intermittent when loaded, and, if possible, should be checked by monitoring for a voltage drop with the system operational (under load).
 
Check the fuses. The cruise control system uses at least one system fuse. The stoplamps are also fused, there may be more than one fuse in the stoplamp circuit and those fuses should also be checked. Don't rely on a visual check. Remove the fuse and check for continuity with an ohmmeter. Remember, the stoplamps and the center high mounted stoplamp must be working for the circuit to the cruise control system to be complete.
 
Check the ground. Most of these system use a black wire with an eyelet crimped on the end. A sheetmetal screw secures this ground to the inner fender, usually on the strut tower, and usually under the cruise control module itself.
 
Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems.
 
If, after these preliminary checks are made and no problem is found, the vehicle should have the system checked by a qualified technician with a scan tool, interrogating the system through the vehicle's Data Link Connector (DLC).
 



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Fig. Underhood wiring and cruise control module arrangement-2000 Grand Prix shown



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Fig. Underdash wiring and cruise switch arrangement-2000 Grand Prix shown



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Fig. Underhood wiring and cruise control module arrangement-2000 Intrigue shown



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Fig. Underdash wiring and cruise switch arrangement-2000 Intrigue shown



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Fig. Cruise control and hazard lamp switch, LH side of instrument panel-2000 Intrigue shown

 
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