TideLog Archive for the “Mercedes Sprinter 2000 – 2006” Category

The Sprinter contains a Sentry Key Immobilizer System (SKIS) which has three main components:

1. A transponder circuit in each key fob, with lock/unlock buttons and integral battery.

2. A transponder ring antenna.

3. A Sentry Key Remote Entry Module (SKREEM) which is wired to the van’s high speed CAN (Controller Area Network) where it can talk to the Engine Electronic Control Unit (EECU or ECU).

The system communicates with the Sentry Key Remote Entry Module (SKREEM), using the transponder chip located within the Remote Keyless Entry (RKE) fob. Ignition keys are supplied with the van when it is shipped from the factory. The SKREEM module is located inside the instrument cluster housing, just under the cluster housing cover, at the back of the cluster unit itself.

The transponder ring is plugged into the SKREEM module, where its wire runs from the instrument cluster up to where the ring itself is slotted over the ignition barrel. It is a wireless radio antenna.

Each Sentry Key has a unique transponder identifcation code permanently programmed into it by the manufacturer. Likewise, the Sentry Key Remote Entry Module (SKREEM) has a unique “Secret Key” code programmed into it from the factory too. 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 permanently 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 determines if a valid key is present based on the information it receives from the Sentry Key. If a valid key is detected, a message is sent to the Engine Control Unit (ECU) via the Controller Area Network (CAN) data bus and the vehicle is allowed to start or continue running. If an invalid key is received by the ECU or no status at all is communicated, the engine will stall after two (2) seconds of running because the ECU cuts power to the glow plugs and fuel injectors. The indicator light on the key fob 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 include:
a. Two transponder keys too close together.
b. Speed Pass too close to transponder key.
c. Solid indicator in the instrument cluster indicating there is a system failure.
d. Loss of ECM communication on the CAN bus, either due to interference or faulty control unit.
e. Failed transponder ring circuit.

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My company pride and joy is back on the road after her little accident a few months ago (I rolled her over after a tyre blew out on the motorway) It’s my company van, my Mercedes Sprinter 311CDi, in case you were wondering what I was talking about! She’s been at Mercedes for the past 2 months, having all the chassis straightened out, and having a respray.


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