SPEED CONTROLE

Description and Operation System Diagram Item Description 1 Control switch unit - cruise control system Refer to Component Description: Speed control switch(es). 2 Clockspring 3 Instrument cluster 4 wheel speed sensor, 5 ABS (anti-lock brake system) module 6 TCM (transmission control module) Comments: Vehicles with automatic transaxle. 7 PCM (powertrain control module) 8 Throttle body Comments: Contains the TP (throttle position) sensor 9 The APP (accelerator pedal position) sensor. 10 CPP (clutch pedal position) switch Comments: Vehicles with manual transaxle. 11 BPP (brake pedal position) switch System Operation Speed Control The cruise control system is integrated into the PCM and intervenes in engine management to automatically maintain the target speed selected by the driver. When the system is active, the vehicle can be accelerated or decelerated without the accelerator pedal being pressed. The PCM controls the throttle to achieve this. The ABS module supplies the VS signal required to do this. The cruise control system is operated using the control switch unit on the steering wheel. On vehicles with an automatic transmission, the TCM receives notification over the CAN (controller area network) bus that the cruise control system has been activated. The TCM then controls the transmission based on special engine maps. The cruise control system recognizes three operating modes: "OFF": The system is switched off. "STANDBY": The system is switched on but is not currently controlling the speed of the vehicle. "ACTIVE": The system is switched on and is adjusting the vehicle speed to match the speed set by the driver. Every time the engine starts, the cruise control system is "OFF". Only the "ON" rocker switch is operational in this state. The cruise control system is initially placed in "STANDBY" mode by pressing the "ON" rocker switch. The speed control system is then in "STANDBY" mode. No speed has been saved. The cruise control system can only be put into the "STANDBY" mode under the following circumstances: Engine speed between idle speed and maximum permissible speed. In the "STANDBY" mode, only the "OFF", "SET+" and "SET-" rocker switches are operational. The cruise control system can be switched off again by pressing the "OFF" rocker switch. The cruise control system can only be changed into "ACTIVE" mode under the following conditions: 2. - 5. gear engaged. Engine speed between idle speed and maximum permissible speed. Vehicle speed at least 30 km/h. The cruise control system is activated by pressing the "SET+"- or "SET-" rocker switch. The system is in "ACTIVE" mode. The current speed is saved. The "Cruise control" indicator lamp in the instrument cluster lights up. In the "ACTIVE" mode, the "OFF", "SET+" "SET-" and "CAN/RES" rocker switches are operational. The cruise control system can be switched off again by pressing the "OFF" rocker switch. By pressing the "SET+" rocker switch (for a shorter time than 640 ms), the target speed can be increased by 1 km/h increments. If the "SET+" rocker switch is held pressed (for longer than 640 ms), the system increases the target speed continuously until the rocker switch is released. If the rocker switch is not released, the cruise control system accelerates the vehicle up to the maximum permitted speed of the cruise control system (200 km/h) or to the highest speed of the vehicle (whichever is lower). By pressing the "SET-" rocker switch, the target speed can be decreased by 1 km/h increments. If the "SET-" rocker switch is held pressed, the system decreases the target speed continuously until the rocker switch is released. If the "SET-" rocker switch is held pressed until the speed of the vehicle is less than 30 km/h, the cruise control system goes into "STANDBY" mode. The "CAN/RES" rocker switch has a dual function for interrupting or re-activating the system. By pressing the "CAN/RES" rocker switch, the cruise control system is moved into the "STANDBY" mode ("CAN" function). The "Cruise control" indicator lamp in the instrument cluster goes out. The stored speed can be resumed again by pressing the "CAN/RES" rocker switch once more ("RES" function). The "Cruise control" indicator lamp in the instrument cluster lights up. If during the "RES" function (resume the stored speed), the "SET+" or "SET-" rocker switch is pressed, the cruise control system stores the current speed as the target speed. The cruise control system goes into STANDBY mode in the following situations: Operation of the brake pedal Operation of the clutch pedal Handbrake operation If the driver operates the accelerator pedal and the saved speed is subsequently exceeded for more than 5 minutes. Pressing one of the cruise control system rocker switches for longer than 2 minutes Intervention by the traction control or the electronic stability program (for longer than 40 ms) Shifting of the gear selector lever to the "N" position (vehicles with automatic transmission only) Speed falls below 30 km/h. Appearance of certain DTC (diagnostic trouble code) If the accelerator pedal is operated, the speed increases. As soon as the pedal is released, the speed falls to the saved value. The following components supply the signals necessary for the operation of the cruise control system: Accelerator pedal position (APP) sensor - The APP sensor determines the current position of the accelerator pedal and transmits this to the PCM and the instrument cluster. - If one or both of the APP sensors fails, a fault is stored in the fault memory of the PCM and the cruise control system cannot be activated. Brake pedal position (BPP) switch - The BPP switch tells the PCM whether the vehicle is being braked. In its rest state it is closed and it conducts a ground signal to the instrument cluster. This signal is sent to the CAN via the PCM databus. - The stoplamp switch is directly connected to the PCM and is open in its rest state. When the vehicle is braked, the brake light switch sends a signal to the PCM. This compares the signals from the BPP switch and the brake light switch. If a deviation occurs, a fault is stored in the fault memory of the PCM and the cruise control system cannot be activated. Clutch pedal position (CPP) switch - The CPP switch sends a ground signal to the PCM as soon as the clutch is operated. - If the CPP switch is incorrectly installed or set, the cruise control system cannot be activated. Wheel speed sensors - The wheel speed sensors record the speed of the wheels. The recorded speed is sent to the ABS module via a hard-wired connection. The ABS module calculates a vehicle speed signal (VS signal) from the speed and the wheel diameter. This VS signal is then transferred via the CAN bus to the PCM and supplied to the cruise control system. If the VS signal is faulty, the cruise control system cannot be activated. Parking brake switch. - The parking brake switch is hard-wired to the instrument cluster. When the parking brake is applied, the parking brake switch sends a signal to the instrument cluster. The parking brake warning lamp in the instrument cluster comes on. If the parking brake indicator lamp is lit, the cruise control system cannot be activated. Reversing lamp switch - The reversing lamp switch is hard-wired to the GEM (generic electronic module). The reversing lamp switch sends a signal to the GEMwhen reverse gear is engaged. The GEM activates the reversing lamp. The cruise control system cannot be activated when reverse gear is engaged. Component Description Speed control switch(es). Item Description 1 Cruise control system OFF 2 Cruise control system ON (Standby (ON) 3 Acceleration active (Set +) 4 Interrupt cruise control (CAN) / reactivate (RES) 5 Deceleration active (Set –) The cruise control rocker switches are non-locking rocker switches. The circuit to the coil spring is via a hard-wired 16-pole connection. The cruise control system rocker switches are based on the resistance bridge circuit principle. The cruise control system rocker switches provide a variable resistance signal voltage to the clock spring. The cruise control system rocker switches receive a 5 Volt reference voltage. The instrument cluster measures the feedback voltage in order to determine which function of the rocker switches has been selected. A simple measurement of the resistance across pins 8 and 9 of the 16-pin clock spring connector allows the operation of the cruise control system rocker switches to be checked. A change in resistance must occur when a rocker switch is operated.