OK, this is going to be long, so beware! Get yourself a good drink and curl up on the sofa and get ready to read. Hopefully, this will explain everything you ever wanted to know about the MBZ DAS system. I have gathered this information from various official MBZ sources, included technical documentation, service documents, and even authorized technicians and factory personnel. Because this is all â€œdouble-secret inside informationâ€?, I cannot guarantee that everything is 100% accurate, but I donâ€™t believe I am terribly misinformed as does all seem to make sense.
AAM (All-Activity Module) â€“the electronic circuitry that controls all vehicle functions except for engine and transmission systems.
ECM (Engine Control Module) â€“the electronic circuitry that controls all engine functions including ignition delivery and timing, fuel delivery, and fuel/air mixture.
DAS (Drive Authorization System) â€“ the systems used by MBZ vehicles to validate a key for starting the engine. This is also the name of a specific electronic module either built-in to the AAM or attached to the AAM that performs the validation.
EIS (Electronic Ignition Switch) â€“ the ignition switch on models that use the newer â€œbladelessâ€? infrared key.
ESL (Electronic Steering Lock) â€“ an electronic lock that disables the steering column on models that use the newer â€œbladelessâ€? infrared key.
RCL (Remote Control Locking) â€“the function of the key fob that allows the vehicle to be remotely locked and unlocked.
CAN (Controller Area Network) â€“an electronic data bus that allows the different vehicle systems to communicate, i.e. the AAM and ECM exchange data over the CAN.
HHT (Hand Held Tester) â€“ an electronic device used by service technicians to diagnose and program vehicle functions. It connects to the OBDII port and communicates over the CAN.
FDOK â€“ MBZ worldwide database that contains all information about ever MBZ ever built, including the assignment of all electronic key codes for all vehicles using DAS.
PDC (Parts Distribution Center) â€“ MBZ locations where parts are stored. Some of the PDCâ€™s are authorized for the distribution of vehicle keys. Those that are have equipment capable of programming a specific fixed key ID from FDOK into a virgin key fob.
Now, on with the showâ€¦
THE DRIVE AUTHORIZATION FUCNTION:
All Mercedes-Benz vehicles manufactured in about the last ten years use DAS to electronically validate the vehicleâ€™s key. Each key fob for this system contains an EEPROM chip that stores a fixed serial number and a rolling code. Each time the key is used in the ignition switch, DAS reads both the fixed serial number and the rolling code. These values are compared to known valid values stored in DAS. If a match is found, the ECM will allow the engine to start and run, and DAS will write a new â€œrandomizedâ€? rolling code to the key fobâ€™s EEPROM. If the key fails validation, even if it is mechanically able to turn the ignition switch, the ECM will prevent the engine form running.
Every Mercedes-Benz vehicle has a record in FDOK. When the record is created for a new vehicle, a set of unique key serial numbers is assigned and stored in FDOK. Only certain authorized employees at authorized PDCâ€™s have access to this information. Authorized PDCâ€™s stock virgin key transponders and have special equipment to program them with valid serial numbers from FDOK. Keys are programmed when key set is ordered for a new vehicle or an additional or replacement key is ordered for an existing vehicle. Only a factory or an authorized service center can order keys. For existing vehicles, the service center is required to verify that the customer ordering a key is in fact the owner of the vehicle in question. Examining the customerâ€™s photo ID and the vehicleâ€™s registration receipt generally satisfies this.
For new factory vehicles, there is an operation that performs the initial programming of DAS to introduce it to its assigned key set. This loads all the pre-defined key serial numbers into DAS as defined in FDOK. Even though not all keys physically exist, all possible key IDâ€™s for that vehicle are loaded. This is performed in different ways depending on which version of DAS the vehicle uses. Once performed, there is a â€œmarriageâ€? process that irreversibly locks this data into DAS. Once married to a key set, DAS will only recognize keys in that set. Officially, there is no way to reverse this process and introduce a new key set to DAS, nor is there a way to alter any of the individual key IDâ€™s know to DAS.
DIFFERENCES IN VERSION OF DAS:
There are two versions of DAS â€“ version 2 and 3. Version 2 generally uses the rectangular fob and a mechanical â€œswitchbladeâ€? to operate the ignition switch. This is the style key used on all W163 M-Class vehicles. Version 3 almost exclusively uses a tapered fob key with an infrared interface and has no metal blade for the ignition switch. The exception is that MY2002+ W163â€™s use DAS 3, even though they retain the rectangular fob and metal blade ignition key.
The main difference between DAS 2 and DAS 3 is in the way the key is validated. With DAS 2, the key is validated only by the DAS/AAM module, which in turn sends an â€œOK to Startâ€? signal to the ECM via the CAN. With DAS 3, the keyâ€™s ID is actually transmitted over the CAN where the ECM validates it. For the W163 using DAS 3, the keyâ€™s ID is read by the DAS/AAM module and transmitted over the CAN. For other models with DAS 3 that use the infrared interface, the EIS reads and transmits the ID as there is no dedicated DAS â€œmoduleâ€? in these vehicles, although the â€œsystemâ€? is still referred to as DAS. There was also an original DAS version â€œ1â€? that did not use a two-way communication rolling code system.
For all versions of DAS, there is no battery required for the key. The battery in the key fob is used only to power the RCL functions. The power for the DAS functions comes from an electronic coil mounted in the ignition switch housing that supplies inductive current to the circuitry in the key fob. For DAS 2 vehicles (and W163â€™s with DAS 3), this coil is also used to transmit and receive radio frequency signals for reading and writing the keyâ€™s EEPROM. For DAS 3 vehicles (except the W163), the transfer of data between the EIS and the fobâ€™s EEPROM is performed via an infrared signal. Also, since there is no mechanical blade to unlock the ignition switch, the release of both the ignition switch and the steering column lock is performed electronically once DAS validate the key through the infrared data exchange.
KEY CONFIGURATIONS FOR DAS 2:
With DAS 2, there is a maximum of 8 unique keys per vehicle. These key IDâ€™s are programmed into a virgin DAS/AAM module at the factory using the valet key, also known as the â€œOne-Way Masterâ€?. This master key is programmed at the PDC with all eight pre-defined key numbers as assigned to the vehicle in FDOK. At the factory, the master is used along with the HHT to initiate the download of these IDâ€™s. Once the download has taken place, the key set can be married to DAS either by a function on the HHT or after 50 engine starts. The one-way master then becomes one of the valid 8 key numbers and is designated as the valet key. Other than lacking the RCL functions, the valet key has the same EEPROM and programmable rolling code functions as the rectangular fob keys.
When a new key is requested, either because one is lost or the customer desires an additional spare key, it is ordered from the PDC where it is created with the next unused key number according to FDOK. If the key is a replacement for a lost key, the service center technician will disable the key number of the missing key. This can be done as either a reversible or irreversible process. This has no effect on the RCL function; itâ€™s programming is handled separately within the AAM. This means that it is possible to have a key that can function for RCL, but not start the engine. Once all eight key numbers have been created by the PDC, any additional keys would require replacement of the DAS module and the creation of an entirely new key set from the PDC.
KEY CONFIGURATIONS FOR DAS 3:
With DAS 3, there is a maximum of 24 keys per vehicle, however only 8 can be active at a time. Basically, DAS 3 has the same 8 key numbers as DAS 2, but for each key number, there are three key â€œsegmentsâ€?. The valid key numbers and segments are programmed into the virgin ESL, EIS and ECM using a special green-colored â€œworkshop keyâ€?. As delivered, the vehicle will have two keys using key number 1, segment 1 and key number 2, segment 1 (some models were delivered with three keys, the third one using key number 3, segment number 1). When a new key is ordered, the PDC determines which key number and segment to supply based on whether the key is a replacement for a lost one or and additional spare key.
If an additional spare key is requested, then the PDC will create it as the next unused key number, segment 1. If a replacement key is requested, the technician must determine which key number was lost and order its replacement. The PDC will create the replacement with the next unused segment number for that same key number. When the replacement key is first used in the vehicle, DAS will disable the use of the key using the same key number and the previous segment. For example, if key number 2 is lost, the technician orders a replacement for key number 2 and the PDC supplies key number 2, segment 2. When this new key is used in the vehicle, this will disable key number 2, segment 1. Even if that lost key is found, it will no longer operate the vehicle. If key number 2 is lost again, the technician again orders a replacement for key number 2 and the PDC supplies key number 2, segment 3, which disables key number 2, segment number 2. If key number 2 is lost again, the PDC will supply a key with the next unused key number, segment 1, and the technician will be instructed to disable key number 2 completely using the HHT. Note that RCL functions are tied to DAS 3 so no additional programming is necessary to disable a lost key from RCL.
A FEW NOTES:
With DAS 3, virgin components (ESL, EIS and ECM) are shipped with Transport Protection. This allows these devices to function only in a limited test mode until they are authorized using the green workshop key. This would prevent stolen virgin components being used to bypass the DAS security on an existing vehicle.
For the W163 M-Class, the DAS circuitry was integrated into the AAM circuitry for model years 1998 and 1999. Beginning with model year 2000, the DAS circuitry was placed in a separate module that is externally connected to the AAM. This allows for an easier and less expensive replacement of DAS in those vehicles.
As of model year 2002, the W163 M-Class was built using DAS version 3. However, because the older style fob and mechanical key was retained, the system still only allows for eight key numbers with no segment designations. The eight valid key numbers are stored in the ECM and these values are not â€œfield programmableâ€?. The ECM and key set must be ordered together, pre-programmed at the PDC.
It is theoretically possible that with the PDC could create a W163 key that is a â€œcloneâ€? of the serial number of an existing key with the correct mechanical blade. Because the key would not contain the same rolling code as previously assigned by the vehicleâ€™s DAS, it would not be recognized as valid.
There is a way that an in-service DAS version 2 module can be reprogrammed to change the eight key numbers that it recognizes and also to indicate that any or all of those key numbers are â€œvirginâ€? keys so that they do not have to have a valid rolling code. This would be how to use a â€œforeignâ€? key from another vehicle. MB corporate prohibits any authorized service from doing this. Furthermore, there is conflicting information about how this is actually performed. Some data suggests that it can be performed using a certain version of the HHT. Other data suggests that it required removal of the EEPROM form the DAS/AAM and having it â€œmanuallyâ€? programmed using appropriate electronic equipment.
Since DAS version 2 does not have the ECM validate the key (it relies on that validation being performed by the DAS/AAM), it is theoretically possible to simulate the validation over the CAN bus and bypass DAS security. This would require the appropriate equipment to interface with CAN signaling as well as knowledge of the CANâ€™s protocols and functions.
Well, that is all I know about DAS. I hope this information is helpful and that you are still awake!