Mercedes-Benz Sprinter / Dodge Sprinter. Service manual - part 251
TRANSPONDER KEY
DESCRIPTION
The Sentry Key Immobilizer System (SKIS) which
communicates with the Sentry Key Remote Entry
Module (SKREEM), uses a transponder chip that is
integral to each key fob (Fig. 6). Ignition keys are
supplied with the vehicle when it is shipped from the
factory. The transponder chip is located within the
Remote Keyless Entry (RKE) fob.
OPERATION
Each Sentry Key has a unique transponder identi-
fication code permanently programmed into it by the
manufacturer. Likewise, the Sentry Key Remote
Entry Module (SKREEM) has a unique “Secret Key
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code programmed into it by the manufacturer as
well. When a Sentry Key is programmed into the
memory of the SKREEM, the SKREEM stores the
transponder identification code from the Sentry Key,
and the Sentry Key learns the “Secret Key” code
from the SKREEM. Once the Sentry Key learns the
“Secret Key” code of the SKREEM, it is also perma-
nently programmed into the transponder’s memory.
The Sentry Key’s transponder is within the range
of the SKREEM’s transponder ring when it is
inserted into the ignition lock cylinder. When the
ignition switch is turned to the ON position, the
SKREEM communicates with the Sentry Key via a
radio frequency (RF) signal. The SKREEM deter-
mines if a valid key is present based on the informa-
tion it receives from the Sentry Key. If a valid key is
detected, that fact is communicated to the Engine
Control Module (ECM) via the Controller Area Net-
work (CAN) data bus and the vehicle is allowed to
continue running. If an invalid key is received by the
ECM or no status at all is communicated, the vehicle
will stall after two (2) seconds of running. The indi-
cator light will be flashing at this point. The Sentry
Key’s transponder can not be repaired. If it is faulty
or damaged, it must be replaced.
Common communication problems:
• Two transponder keys too close together.
• Speed Pass too close to transponder key.
Solid indicator that there is a system failure.
• Loss of ECM communication.
• Failed transponder ring circuit.
Fig. 6 TRANSPONDER KEY
1 - TRANSPONDER KEY FOB
2 - RKE BUTTONS
3 - INDICATOR LIGHT
4 - KEY BLADE RELEASE BUTTON
5 - KEY BLADE
VA
VEHICLE THEFT SECURITY
8Q - 5