Cruise Control Switches

NOTE: The cruise control system may also be referred to as the speed control system.

The speed control system is electronically controlled and vacuum operated. The electronic control is integrated into the Powertrain Control Module (PCM) which is located in the engine compartment. The controls are located on a single stalk switch. The ON, OFF, RESUME, ACCEL, SET, COAST and CANCEL lever is located on the right side of the steering wheel. The system is designed to operate at speeds above 25 MPH.

When speed control is activated by depressing the ON switch, the PCM allows a set speed to be stored in RAM for speed control. To store a set speed, depress and release the SET switch while the vehicle is moving at a speed between 30-85 MPH. In order for the speed control to engage, the brakes cannot be applied, nor can the gear selector be indicating the transmission is in Park or Neutral (ATX) or 1st/2nd gear (MTX). The speed control can be disengaged manually by preforming one of the following.

Stepping on the brake pedal.
Depressing the OFF switch.
Depressing the CANCEL switch.
Depressing the clutch pedal.
Operating in 1st or 2nd gear (autostick, if equipped).

NOTE: Turning the system off by depressing the OFF switch or turning off the ignition switch will erase the set speed stored in the PCM.

For added safety, the speed control system is programmed to disengage for any of the following conditions.

An indication of Park or Neutral.
A rapid increase RPM (indicates that the clutch has been disengaged).
Excessive engine RPM (indicates that the transmission may be in a low gear).
The speed signal increases at a rate of 10 MPH per second (indicates that the co-efficient of friction between the road surface and tires is extremely low).
The speed signal decreases at a rate of 10 MPH per second (indicates that the vehicle may have decelerated at an extremely high rate).
If the actual speed is greater than 20 MPH over the set speed.
Autostick shifts into 1st or 2nd gear (autostick, if equipped).

Once the speed control has been disengaged, depressing the RESUME switch when speed is greater than 20 MPH allows the vehicle to resume control to the target speed that was stored in the PCM. While the speed control is engaged, the driver can increase the vehicle speed by depressing the ACCEL switch. The new target speed is stored in the PCM when the ACCEL switch is released. The PCM also has a "tap-up" feature in which target speed increases by 2 MPH for each momentary switch activation of the ACCEL switch. The PCM also provides a means to decelerate to a new lower target speed without disengaging speed control. Depress and hold the COAST switch until the desired speed is reached, then release the switch. The PCM also has a "tap-down" feature in which target speed decreases at 1 MPH for each momentary switch activation of the coast switch.

Climbing A Grade - When climbing a grade the interactive speed control tries to maintain the set speed by increasing the throttle opening, while inhibiting/delaying downshifts. If opening the throttle alone cannot maintain the set speed and the vehicle speed drops more than 3 MPH below the set speed, the transmission will downshift to third gear. If the vehicle continues to lose speed, by more than 6 MPH, the transmission will downshift again to maintain the set speed. After the vehicle encounters a less-steep grade, or has crested the grade (reduced the load on the powertrain) and can maintain the set speed at a reduced throttle position, the transmission will upshift, as appropriate, until the set speed can be maintained in Overdrive.

Grade Hunting - All vehicles equipped with a four speed automatic transmission have a grade hunting feature for the 2nd to 3rd gear upshift and the 3rd to Overdrive upshift. The PCM identifies the powertrain loading conditions and selects the proper gear to maintain the current vehicle speed. Under moderate loading conditions the transaxle will stay in 3rd gear until the top of the grade is reached or the powertrain loading is reduced. If powertrain loading is severe, the transaxle may shift into 2nd gear and remain there until powertrain loading is reduced, then a 2nd to 3rd gear upshift will be scheduled. Grade hunting features always operate regardless of whether or not the interactive speed control is engaged. If the interactive speed control is not engaged and powertrain loading is not reduced, the driver may have to completely lift off of the throttle before an upshift will occur. If the driver does lift off the throttle to induce an upshift under these conditions, vehicle speed will reduce and the Overdrive to 3rd and 3rd to 2nd gear downshifts will reoccur when the throttle is reapplied. If grade hunting is repeatedly induced by the driver, transaxle damage may result.

Automatic Speed Control Overspeed Reduction - Transmission control software includes an automatic speed control overspeed reduction feature. This maintains vehicle speed at the selected set point when descending a grade. The PCM first senses that the speed control is set. If the set speed is exceeded by more than 4 MPH and the throttle is closed, the PCM causes the transaxle to downshift to THIRD gear. After downshifting, the automatic speed control resumes normal operation. To ensure that an upshift is appropriate after the set speed is reached, the PCM waits until the speed control system opens the throttle at least 6 degrees before upshifting to OVERDRIVE again. If the driver applies the brakes, canceling automatic speed control operation with the transaxle still in THIRD gear, the PCM maintains this gear until the driver opens the throttle at least 6 degrees to avoid an inappropriate upshift. The upshift is also delayed for 2.5 seconds after reaching the 6 degrees throttle opening in anticipation that the driver might open the throttle enough to require THIRD gear. This will avoid unnecessary and disturbing transmission cycling. If the automatic speed control RESUME feature is used after braking, the upshift is delayed until the set speed is achieved to reduce cycling and provide better response.