Experiencing issues with your 1996 Mercedes-Benz S320 remote locking system? It can be a frustrating problem when your key fob refuses to communicate with your car, especially when the central locking from the console works just fine. If you’re starting to troubleshoot this issue, understanding the role of the AAM (All Activity Module) and checking related fuses, including the antenna fuse, is a crucial first step. While fuse issues are often the culprit in electrical problems, sometimes the solution is more complex, as one owner discovered with their S320.
Initially, the owner of a ’96 S320 faced a common problem: the remote key fob would not lock or unlock the doors, even after trying a used remote with the key blade and RFID chip transplanted. This eliminated the possibility of a simple remote malfunction. Seeking expert advice, they meticulously traced the circuits, ruling out relay contact or wiring problems. It was confirmed that the lock/unlock command circuit from the AAM was functioning correctly, as the console lock switch operated without issue. This pointed away from a general wiring fault and towards a more specific module problem.
Suspicions began to fall on the AAM itself. Despite other functions of the AAM operating normally, the possibility of a faulty radio receiver section within the module emerged. Even swapping out the antenna to eliminate it as the source of the problem yielded no positive results. This process of elimination is critical in diagnosing complex automotive electrical issues.
To further investigate, the owner took their S320 to a Mercedes-Benz dealership for a professional diagnostic session using their specialized SD (Star Diagnosis) system. The diagnostic scan revealed intermittent communication problems with the AAM, suggesting internal issues within the module. Witnessing the diagnostic process firsthand provided valuable insight into the complexity of modern car electronics and the capabilities of dealer-level tools.
Based on the diagnostic findings, the decision was made to replace the AAM. The replacement procedure involved a few key steps, efficiently executed by the dealer’s experienced technician. First, the existing AAM’s configuration settings were backed up using the SD system – a process that took around 15 minutes. Physically replacing the AAM was straightforward, taking only 10 to 15 minutes. Finally, programming the new AAM involved simply transferring the saved configuration settings, a process of checking boxes within the SD system, which was completed in approximately 20 minutes.
Immediately after the AAM replacement and programming, the car’s remote locking system sprang back to life, syncing with both remotes and functioning flawlessly. This experience highlights that an AAM can indeed be partially faulty, affecting specific functions like remote locking while leaving others operational. While initially one might consider fuse locations for the AAM or antenna – and checking these is a good preliminary step in any electrical troubleshooting – in this case, the root cause was a deeper internal failure within the AAM itself, requiring module replacement for a complete fix.
For owners of a 1996 Mercedes-Benz S320 experiencing similar remote locking problems, this case study provides a valuable troubleshooting path. While fuse locations for the AAM and antenna should be checked initially (typically found in the fuse box under the hood or in the driver’s side footwell – consult your owner’s manual for precise locations and diagrams), if these are intact, a deeper diagnostic investigation, potentially pointing towards AAM issues, might be necessary to restore full remote locking functionality. Consider professional diagnostic services to pinpoint the exact cause and ensure correct repair procedures.
