OK ! ELECTRONIC CRUISE CONTROLOn late model vehicles with electronic throttle control, the cruise control system is fully electronic. The cruise control switch on the steering wheel or steering column sends your inputs to the Body Control Module (BCM), which then passes it along to the Powertrain Control Module (PCM), unless the system is wired to send your inputs directly to the PCM via dedicated wiring or the controller area network (CAN) bus. The PCM notes the speed setting you requested when you turned the cruise control system on. It then looks at the actual vehicle speed via the input from the transmission vehicle speed sensor(VSS). The PCM then calculates how much throttle is needed to maintain the requested speed. The PCM then commands the actuator motor on the throttle shaft to open or close the throttle to increase or decrease engine RPM and vehicle speed so the actual speed matches the requested speed. The PCM also monitors inputs from the transmission (so it knows what gear the transmission is in), and the position of the brake pedal (so it can temporarily deactivate cruise control when you step on the brakes). Depending on the sophistication of the system, it may also look at inputs from the ABS (antilock brake) system and/or stability control system. When the cruise control system is engaged, the PCM also monitors the position of the throttle and/or accelerator pedal. If you step on the gas to pass another car, your foot temporarily overrides the cruise control system's set speed. When you release the accelerator pedal, your car will decelerate and resume the previous speed setting. CRUISE CONTROL WON'T ENGAGEThe cruise control system will NOT engage if any of the following conditions are present: * The transmission is in Park, Neutral, Reverse or Low gear * The clutch is disengaged (clutch pedal depressed) * The vehicle is traveling less and 25 to 30 mph (varies depending on year/make/model of vehicle) * The driver is holding his foot on the brake pedal (or the brake pedal switch is showing a constant application of the brakes) * There is no input from the vehicle speed sensor (which will also prevent the speedometer from working) * Engine speed and/or throttle position does not match the commanded position * Electrical voltage to the PCM or other components in the system is too low (less than 9 volts) * The ABS or Traction Control system has been active for more than two seconds (this may vary depending the application) * Vehicle speed is excessive (some cruise control systems are programmed NOT to work above a certain maximum speed for safety reasons (typically 90 mph or faster) * The system's self-diagnostics has detected a fault and set a code. This will deactivate the system and prevent it from functioning until the fault is diagnosed and repaired.