Cruise Control Module
Cruise control module (2) is located to right of instrument panel compartment. See Fig 1 . Main function of cruise control module is to monitor and act upon input signals from cruise control switch and Vehicle Speed Sensor (VSS).
There are 4 different categories of input signals received by cruise control module. These 4 categories are on-off, speed control, throttle position and cancel. On-off input signal to cruise control module is provided by cruise control switch and simply activates and de-activates cruise control system. Speed control input signals to cruise module are provided by cruise control switch and VSS. Speed control input signals are provided by cruise control switch are RES/ACC (Resume/Accelerate) signal and SET/COAST signal.
These signals are also used to initiate tap-up and tap-down functions. Cruise control module uses these signals, in addition to vehicle speed signal from VSS, to determine and maintain or alter vehicle speed in accordance with driver's commands. Throttle position signals to cruise control module are provided by cruise control servo and idle switch inside Throttle Position (TP) sensor. These signals, as their names suggest, allow cruise control module to constantly monitor throttle position during cruise control system operation. Cancel input signals to cruise control module are provided by cruise control switch CANCEL signal, brakelight switch, PNP switch, or cruise control release switch. These input signals inform cruise control module that cruise control operation should be immediately suspended.
Output signals from cruise control module are all sent to cruise control servo and will vary depending upon type of input signals received. If, for example, cruise control module senses that vehicle speed has dropped below desired cruise speed, an output signal will be sent to, open throttle, side of DC motor within cruise control servo. This action will cause motor to turn worm gear, open throttle, and increase vehicle speed until desired cruise speed is activated. If cruise control module should sense that vehicle speed is above desired cruise speed, an output signal is sent to, close throttle, side of DC motor within cruise control servo. This action will cause motor to turn in opposite direction, close throttle, and decrease vehicle speed until desired cruise speed is achieved.
Finally, should a cancel input signal be received, cruise control module de-energizes magnetic clutch within cruise control servo. This action disengages DC motor from worm gear, causing throttle to go to idle position and effectively canceling cruise control operation. Cruise control module also has a self-diagnostic capability. In conjunction with cruise control switch, it can be used to run an abbreviated self-test which covers all cruise control switch positions, brakelight switch, PNP switch, cruise control release switch, and VSS. In addition to abbreviated self-test, grounding No. 11 (Tc) terminal in Data Link Connector (DLC) allows cruise control module to flash Diagnostic Trouble Codes (DTCs) on CRUISE control indicator. By reading DTCs and following diagnostic tables, any electrical problem in cruise control system can be identified and repaired