Key identification and start processes
- Ignition key at position 2: The transponder receives electrical energy from the ring antenna and responds by transmitting the key data to the EWS control unit.
- The EWX control unit must verify the key data before it will transmit a release signal to engine management and starter:
On vehicles with automatic transmisssion, the system also requests the position of the transmission selector lever, releasing the starter only with the lever at position P or N.
- Once the engine starts, the EWS control unit generates new key data, which it then transmits to the transponder.
- The starter is deactivated when the EWS control unit monitors a specified engine speed for a defined period of time. This engine-speed limit varies according to the engine installed.
Caution!
For security reasons, the EWS control unit features a defined standby period, which varies according to code (typical standby period: 10 s.). The standby period starts to elapse as soon as the ignition lock returns to position 0and
provided that no diagnosis telegrams are transmitted to the EWS control unit.
The EWS control unit does not
request key data from the key during the standby period. This means that, e.g., if the initial key is exchanged for any other key of the correct physical pattern (even an electronically defective one!) during this period, then this second key can also be used to start the vehicle!
Check keys as follows:
- If the DIS or MoDiC service tester is connected: Disconnect the diagnosis plug from the vehicle.
- Return the ignition lock to position 0 and extract the key.
- Wait for the standby period to elapse; the ignition lock remains at position 0!
- Insert the key to be tested, ignition lock in position 2.
- Attempt to start the vehicle.
The length of the standby period is available in the EWS control unit diagnosis program as "Self-activation time" under "Service functions," "Read code data."
Note
For enhanced safety, the start release also opens the central loking system (if loked).