Specifications

16
Testing Testing DAS (Immobilizer) Systems
(IFZ) was introduced in late 1992 as a standard feature. With central locking, lock actuators are
no longer connected electrically, therefore the central locking, anti-theft, and convenience
systems can no longer be operated with the mechanical key. Instead, a remote control module
operates the complete vehicle locking system through the pneumatic control module. This
keyless entry system consists of a remote control module, transmitter, pneumatic control module,
and two receivers.
The infrared remote control can only be operated with a vehicle-specific transmitter as they are
matched to one another. The remote control transmitter signal consists of a fixed code that must
match the receiver. The code is “rolling,” which means it is changed each time it is actuated.
NOTE:
i The mechanical key can still be used in emergency to open the driver's door or trunk. All door
locks are equipped with micro switches which should disable the anti-theft alarm (ATA) if the
correct key is used to unlock the door. If the ATA does not disarm, insert the key into the ignition
and turn the ignition switch to the ON position.
DAS Versions
In approximately 1991, the ATA system added the K38 relay which controlled starter motor
operation. In approximately 1993, this function was added to the RCL control module,
introducing the immobilizer system which added additional RCL control functions: interruption of
ignition, fuel, starter or vacuum. The important difference is that the RCL control module
communicates on a CAN bus to other control modules.
NOTE:
i If the vehicle is unlocked with the mechanical key, the ignition switch may not operate to start the
vehicle. The vehicle may need to be unlocked using the remote key to unlock the immobilizer,
which then permits the engine to start.
DAS 2
DAS 2 integrated the immobilizer function and engine control into one system. Activation and
deactivation occurs whenever the car is locked or unlocked either with the remote transmitter or
the mechanical key.
This system introduced the rolling code for the remote control on the C, E and S/SL class in
1996. Rolling code changes the access code each time the transmitter (in the remote key) and
receiver (in the vehicle) communicate. Once the receiver authorizes the received code, it sends
a new code back to the remote key.
The engine and DAS control modules are locked together with a common identification code that
cannot be erased. Engine and DAS control modules have to be version coded if replaced.
Table 4-2 DAS 2 characteristics
Triggered By Signal Type
Authorization
Checked By
Operator
Feedback
Authorized
Start Result
Remote or door
and trunk
switches
Remote locking
IR or door and
trunk switches
RCL N-54 Mirror LEDs
NO fuel
injection