Experiencing frustrating communication problems with Mercedes-Benz FBS4 systems when using Xentry? Many technicians encounter scenarios where diagnosing FBS4 equipped vehicles becomes a significant hurdle, especially when faced with a complete lack of module communication. This article delves into a real-world diagnostic challenge, focusing on a Mercedes-Benz truck exhibiting exactly these symptoms, and explores potential troubleshooting steps with an emphasis on Xentry Fbs4 Diagnosis.
A technician recently encountered a Mercedes-Benz truck, a bank repo with an unknown history, presenting a perplexing no-start condition and complete communication failure. The vehicle came with two FBS4 keys, which mechanically unlocked the doors, suggesting key compatibility. However, upon battery connection, an alarm was triggered and could not be deactivated via the key fob or EIS.
After the alarm subsided, peculiar symptoms emerged whenever the driver’s door was opened or parking lights were activated. The instrument cluster illuminated, displaying mileage along with a concerning message: “Transmission not in park risk of vehicle rolling away,” despite the transmission being physically in park. This message persisted regardless of whether the DSM or TCM was connected.
Functionality was severely limited. Only the rear hatch release button, power seats, hazard lights, and interior lights were operational. Notably absent were any dashboard warning lights (engine, ESP, etc.), and inserting or turning the key yielded no ignition response whatsoever.
Initial investigations included replacing the auxiliary battery and confirming the main battery’s health. A thorough fuse and relay check, encompassing all fuse boxes and pre-fuses, revealed no issues. CAN network resistance was tested and found to be within the expected 60-ohm range.
Despite these checks, communication with any module using either Xentry or Autel diagnostic tools proved impossible. Even attempting the FBS4 system test within Xentry’s special procedures resulted in a communication failure. Power supply to the EIS and SAM modules was confirmed.
Attempts to bench-read the EIS using both CGDI MB and Xentry were unsuccessful. While the technician acknowledged uncertainty regarding FBS4 EIS bench reading procedures compared to FBS3, key reading was possible and indicated functional keys. Experience with FBS3 systems allowed for module virginizing, programming, and cloning, but FBS4 capabilities seemed limited to key reading.
The primary suspicion fell on the EIS/EZS as the source of the problem. However, several unanswered questions remained: Why were door lock functions inoperative via both the door switch and key fob? Why was the COMMAND system unresponsive? Why was the steering column inactive? And crucially, why was the “transmission not in park” message displayed incorrectly?
The technician sought advice on further diagnostic tests and methods to “wake up” the CAN network to establish communication with other modules. Questions arose regarding VVDI’s FBS4 capabilities and the potential for using an EIS FBS4 from another W166 chassis vehicle for diagnostic purposes. The feasibility of installing and programming a new OEM EIS/EZS and the required subscription level were also queried, along with whether existing keys could be utilized with a new EIS.
Further complicating the diagnosis, disconnecting CAN connectors at each network bar in the front passenger footwell, one by one, did not resolve the communication issues.
This detailed account highlights the complexities of xentry fbs4 diagnosis when facing a complete communication breakdown. Troubleshooting such issues requires a systematic approach, expert knowledge of Mercedes-Benz FBS4 systems, and potentially advanced diagnostic tools and procedures beyond standard practices. For professionals encountering similar challenges, exploring advanced FBS4 diagnostic techniques and seeking expert forums or resources specializing in Mercedes-Benz systems may prove invaluable in resolving these intricate no-communication scenarios.
