Speed Control - Speed Control—Gasoline - System Operation and Component Description

Description and Operation System Diagram Item Description 1 Control switch units - Cruise control system Refer to Component Description: Cruise control system switches 2 Steering wheel module Comments: Contains the coil spring 3 GEM (generic electronic module) 4 Instrument cluster 5 Wheel speed sensor. 6 ABS (anti-lock brake system) module 7 TCM (transmission control module) Comments: Vehicles with automatic transaxle. 8 PCM (powertrain control module) 9 Throttle body Comments: Contains the TP (throttle position) sensor 10 APP (accelerator pedal position) sensor 11 CPP (clutch pedal position) switches Comments: Vehicles with manual transaxle. 12 BPP (brake pedal position) switches 13 Reverse gear solenoid Comments: Vehicles with manual transaxle. System Operation Cruise control Cruise control is integrated into PCM and intervenes in engine management to automatically keep to 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 cruise control system is operated using the control switch units on the steering wheel. The PCM controls the throttle to achieve this. The ABS module supplies the VS signal for this. On vehicles with automatic transmission, the TCM receives a notification via the CAN (controller area network) bus that the cruise control system is active. 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". In this mode, only the "ON" button is active. The cruise control system is initially set to "STANDBY" mode when the "ON" button is pressed. The corresponding message appears in the instrument cluster. The cruise control system is then in "STANDBY" mode. No speed has been saved. The cruise control system can only be set to "STANDBY" mode under the following conditions: Engine speed between idle speed and maximum permissible speed. In "STANDBY" mode, only the "OFF", "SET+" and "SET-" buttons are active. Pressing the "OFF" button switches the cruise control system back off again. The cruise control system can only be changed into "ACTIVE" mode under the following conditions: 2nd - 6th gear engaged. Engine speed between idle speed and maximum permissible speed. Vehicle speed at least 30 km/h. Pressing the "SET+" or "SET-" button activates the cruise control system. The system is in "ACTIVE" mode. The current speed is saved. The saved speed is displayed in the instrument cluster. The corresponding message appears in the instrument cluster. The green "Cruise control" indicator lamp in the instrument cluster lights up. In "ACTIVE" mode the "OFF", "SET+", "SET-" and "CAN" buttons are active. Pressing the "OFF" button switches off the cruise control system. Tapping the "SET+" button (for less than 640 ms) increases the target speed by 1 km/h at a time. Holding down the "SET+" button (for longer than 640 ms) increases the target speed until the button is released. If the button is not released, the cruise control system accelerates the vehicle up to the maximum permissible speed for cruise control (200 km/h) or up to the vehicle's maximum speed (whichever speed is lower). Tapping the "SET-" button (for less than 640 ms) reduces the target speed by 1 km/h at a time. Holding down the "SET-" button (for longer than 640 ms) reduces the target speed until the button is released. If the "SET-" button is held down until the minimum speed of 30 km/h is reached, the cruise control system switches to STANDBY mode. Pressing the "CAN" button sets the cruise control system to "STANDBY" mode. The last speed saved is then displayed in brackets on the instrument panel. The saved speed can be re-activated by pressing the "RES" button. The speed is displayed in the instrument cluster without brackets. If the "SET+" or "SET-" button is pressed while the "RES" function is being carried out (reactivation of saved speed), the cruise control system saves 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 a cruise control button for more than 2 minutes Intervention by the traction control or 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. Occurrence of particular 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 signals which are required to operate the cruise control system: Accelerator pedal position (APP) sensor - The APP sensor identifies the current position of the accelerator pedal and sends a PWM (pulse width modulation) signal to the PCMand an analog DC (direct current) signal to the GEM. - If one or both of the APP sensors fails, a fault is stored in the PCM fault memory 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 the switch is closed and sends an earth signal to the GEM. This signal is sent via the CAN to the PCM. - The brake light switch is likewise connected to the GEM and is opened in the rest state. When the vehicle is braked, the brake light switch sends a signal to the GEM. This compares the signals from the BPP switch and the brake light switch. If a deviation occurs, a fault is stored in the GEM fault memory and the cruise control system cannot be activated. Clutch pedal position (CPP) switch - The CPP switch sends a ground signal to the GEM as soon as the clutch is operated. This signal is passed on by the GEM via the CANbus to the PCM. This then supplies the signal to the cruise control system. - 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 GEM. The parking brake switch sends a signal to the GEM when the parking brake is operated. The GEM activates the parking brake indicator lamp in the instrument cluster. 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. The reversing lamp switch sends a signal to the GEM when reverse gear is engaged. The GEM activates the reversing lamp. The cruise control system cannot be activated when reverse gear is engaged. Adjustable Speed Limiter Device This system offers the driver the facility to preselect a specific maximum speed which can then no longer be exceeded unintentionally. For example, to stay below the speed limit of a road, or below a highest maximum speed which the driver has decided on. The setting range available is from 30 to 180 km/h. To select the speed, the driver uses the extended control panel on the steering wheel. The maximum speed set by the driver is shown in the instrument cluster together with an integrated symbol for the system. If the vehicle approaches the maximum speed which has been preset by the driver, the engine management system intervenes in a regulatory manner and prevents any acceleration which exceeds it. If more power is needed, for example for an imminent overtaking maneuver, then the speed limiter can be overridden in the short term by a distinct accelerator pedal command. For this intentional override of speed limitation, the accelerator pedal must be moved to more than its 90% position. In this case the display symbol in the instrument cluster will be struck through until the vehicle speed is again below the set speed. There is no warning tone if the set speed is intentionally exceeded ! If the set speed is unintentionally exceeded, (e.g. when descending a hill), the indicator lamp in the instrument cluster flashes and a warning tone sounds. This continues to occur until the speed of the vehicle drops below the set speed again. Component Description Cruise control system switches Item Description 1 Cruise control system ACTIVE/STANDBY (ON) 2 Cancel cruise control (CAN) 3 Cruise control system OFF 4 Acceleration (set +) 5 Reactivate (RES) 6 Deceleration (set –) The cruise control system buttons are non-locking push buttons. They are connected to the coil spring via a hard-wired 16-pin plug connection. The cruise control system buttons are based on the resistance bridge circuit principle. The cruise control system buttons deliver a variable resistance signal voltage to the steering wheel module. The cruise control system buttons receive a 5 Volt reference voltage. The steering module measures the feedback voltage to determine which button has been pressed. A simple resistance measurement across pins 15 and 16 (right cruise control system button) or pins 15 and 8 (left cruise control system button) at the 16-pin coil spring connection enables the function of the cruise control system buttons to be monitored. A change of resistance must occur when a button is pressed. Adjustable speed limiter device switches Item Description 1 Cruise control system switch 2 Adjustable speed limiter device switch