The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2016 S550 Key Not Detected - Passive Entry Failing

0

Mike T. · rep 0 · May 25, 3:07 AM · 1 replies · solved · Question

Vehicle: 2016 Mercedes-Benz S550

Hi all,

I'm having a persistent issue with my 2016 Mercedes-Benz S550 (W222 chassis) and its keyless go system. For the past few days, I frequently get the 'Key Not Detected' message on the dashboard, even when the key fob is clearly inside the car. This makes starting the car a hassle, often requiring me to place the key directly into the emergency slot.

Also, the passive entry (unlocking by touching the door handle) is intermittent or completely failing on all doors. I've replaced the battery in both of my key fobs, but the problem persists. It's really frustrating on a luxury car like this.

Could this be an antenna issue, or maybe something with the car's EIS (Electronic Ignition System)? Has anyone else dealt with this on their S-Class? Any insights or common solutions would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:07 AM

0

ClearTheCode admin answer:

Your experience with the 'Key Not Detected' message and failing passive entry on your 2016 Mercedes-Benz S550 points to a common set of issues related to the Keyless Go/Entry system. While you've correctly addressed the key fob batteries, the problem likely lies within the vehicle's receiving system.

  1. Causes:

    • Keyless Go Antennas: Mercedes vehicles have multiple antennas located throughout the cabin and exterior (e.g., in the door handles, trunk, center console) that detect the key fob's signal. If one or more of these antennas fail or their wiring is compromised, the car won't reliably detect the key.
    • Keyless Go Control Module: This module processes the signals from the antennas. A fault in this module can lead to intermittent or complete failure of the Keyless Go functions.
    • EIS (Electronic Ignition System) or EZS (Electronic Ignition Switch): While less common for intermittent key detection issues, a problem with the EIS/EZS module, which authenticates the key, can also cause these symptoms.
    • RF Interference: Less likely if it's a consistent issue, but external radio frequency interference can sometimes disrupt key fob signals.

  2. Diagnostics:

    • Mercedes-Specific Scan: A standard OBD-II scanner won't typically show codes for Keyless Go system faults. A Mercedes-Benz diagnostic tool (XENTRY/DAS) is required. It can read specific B-codes (Body codes) or U-codes (Network codes) related to the Keyless Go module, antennas, or EIS. Examples might include codes indicating signal loss from specific antennas or a module malfunction.
    • Check All Fobs: Even though you replaced batteries, confirm both fobs exhibit the same behavior. If one works better, it might point to an issue with the specific fob (even if battery is new).
    • Location Testing: Try to pinpoint if the issue is worse in specific areas of the car (e.g., key not detected in the trunk, but detected in the front seat). This can help narrow down which antenna might be faulty.

  3. When to See a Shop:

    • Professional Diagnosis Required: Given the complexity of the Keyless Go system and the need for specialized diagnostic tools, this is definitely a job for a Mercedes-Benz dealership or a specialized independent shop. They can accurately identify which antenna or module is faulty and perform any necessary programming or calibration after replacement. Attempting a DIY fix without proper diagnosis is likely to be frustrating and unsuccessful.
Menu

Help & account