Comfort Start

Comfort Start




The comfort start makes easy engine starting possible because the starter remains automatically activated until the engine is running (rpm signal). Security is enhanced by using the CAS Module with coded keys and the ignition starting button (integral).

When starting to the engine, the CAS contains the data for the EWS code which is transferred to the ECM. The transmission of EWS data between the CAS and the ECM is over the data line D - EWS. Terminal R and terminal 15 is directed by the CAS for all electrical systems. The CAS also activates KL15 WUP (Wake UP) for control modules on the PTCAN.

When KL15 WUP is activated, the control modules change from the state of rest into the operating condition. During the starting procedure, KL50L for the comfort starting relay (in the IVM) and KL50E is switched to the ECM for the starting request. The ECM will activate a ground signal to the comfort starting relay to energize the starter motor.

The brake light switch is monitored by the ECM for the comfort start feature as well as cruise control. An engine start is possible only if the brake pedal is pressed. For safety reasons, the CAS monitors both signals of the brake light switch (the actual brake light switch and the brake light test switch).

The selector lever of automatic transmission must be in position P or N. The position of the selector lever is detected from the direct hardwire signal or via a CAN signal.




Actuation Time of Terminal 50: The monitored actuating times of terminal 50 protects the starter against overloading. The actuation times of terminal 50 are:

- A maximum of 21 seconds. A repetition is possible immediately.
- The actuation time is reduced for each repetition by 2 seconds until the minimum actuation time of 3 seconds is reached.
- If the start/stop button is pressed for longer than the preceding actuation time, the actuation time is increased by 2 seconds again (up to a maximum of 21 seconds).

Switching off the Engine: The vehicle engine is switched off when the vehicle is stopped and the start/stop button is pressed. If the start/stop button is pressed for longer than 2 seconds, the vehicle engine is switched off and then the key is automatically released and pushed out with spring pressure ("convenience off").

Incorrect Operation and "Emergency On": To ensure the safety of the vehicle in the case of an accidental engine shutdown during driving, the "Emergency On" function is available. An engine shutdown during driving can be caused by accidentally pressing the start/stop button (the button must be pressed for at least 1 second or 3 times consecutively).

The "Emergency On" function enables the starter to be actuated again without brake operation at a vehicle speed above 5 km/h (3 mph). The "Emergency On" function also prevents terminal R from being switched off during driving.

Service Functions: When replacing the ECM and/or CAS Module, the following must be completed:

The Service Function "DME/DDE - CAS alignment" in the DISplus. After the alignment the two modules are rigidly assigned to each other and the vehicle.


NOTE: It is not possible to exchange these control modules with another vehicle for testing purposes.