Systems

The speed control system obtains vehicle speed information from the vehicle speed sensor. In most cars and trucks the sensor is mounted on the transmission or in-line with the speedometer cable. The sensor is driven from gearing in the transmission. On 1986-90 Lincoln Town Car, Crown Victoria, Grand Marquis and Mark VII vehicles the speed signal comes from a speed sensor located in the Electronic Instrument Cluster. If the speedometer system is erratic or inoperative, it must be serviced before the speed control evaluation. If the vehicle hesitates, stumbles, surges or has poor acceleration for any other reason, the problem may appear worse in the speed control mode. The driveability concerns must be serviced before the speed control system is evaluated.

The speed control system also interacts with the brake system, and with the clutch system on manual transmission vehicles. Speed control requires electrical continuity through the stoplamps (and clutch switch on manual transmission vehicles) in order to operate. Proper stoplamp operation is required if the system is to disengage with brakes. Proper clutch switch operation is also required on manual transmission vehicles if the system is to disengage with clutch pedal actuation. Stoplamp and clutch switch circuit diagnosis is detailed in Section 37-05 of the appropriate Shop Manual.

NOTE: SPEED CONTROL WILL NOT DISENGAGE IF THE GEARS ARE SHIFTED ON A MANUAL TRANSMISSION VEHICLE WITHOUT DEPRESSING THE CLUTCH PEDAL.