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Key Fob Not Detected / Comfort Access Failure - 2019 X3 M40i

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Kim L. · rep 0 · May 22, 4:07 AM · 1 replies · solved · Question

Vehicle: 2019 BMW X3 M40i

Hi all,

I'm having a really annoying problem with my 2019 BMW X3 M40i (G01). Lately, the key fob isn't being detected reliably. Sometimes I have to hold it right up to the steering column to start the car, and other times it just won't detect it at all. The comfort access feature (unlocking by touching the door handle) has also completely stopped working.

I've replaced the battery in the key fob multiple times, but it hasn't made any difference. It's getting frustrating having to manually unlock the car and then struggle to get it to start. Has anyone else experienced this with their G01 X3? Could it be an antenna issue, or something with the car's access system? Any advice would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:07 AM

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ClearTheCode admin answer:

Your 2019 BMW X3 M40i (G01) experiencing key fob detection issues and comfort access failure points to a problem within the Car Access System (CAS) or the Front Electronic Module (FEM), which manages these functions. This is a common concern for BMW owners.

  1. Key Fob Battery: While you've replaced it, ensure you're using a high-quality CR2032 battery and that it's inserted correctly. A weak or incorrect battery can cause intermittent issues.
  2. Vehicle Battery Health: As with many BMW electrical issues, a weak 12V car battery can cause various modules to malfunction, including the CAS/FEM. Have your main vehicle battery tested.
  3. Comfort Access Antennas: The comfort access system relies on several antennas located throughout the vehicle (e.g., in door handles, trunk, interior). If one or more of these antennas fail or their wiring becomes damaged, the system won't detect the key fob properly. Fault codes like A0A900 (Antenna, interior, short circuit to ground) or A0A901 (Antenna, exterior, short circuit to ground) are common.
  4. Door Handle Electronics: The comfort access system integrates sensors and electronics within the door handles. Moisture ingress or internal failure of a door handle can disable the entire comfort access system. Sometimes, only one handle fails, but it can affect the whole system.
  5. CAS/FEM Module: The Car Access System (CAS) or Front Electronic Module (FEM) is the central control unit for key recognition, starting, and comfort access. A rare but possible internal fault within this module could cause your symptoms. Fault codes related to internal module errors or communication issues (e.g., D90D04 for FEM communication) might be present.

When to See a Shop: Given that you've already addressed the key fob battery, the next step is to have your X3 M40i professionally diagnosed. A BMW specialist or dealership can use diagnostic software (ISTA) to read specific fault codes from the CAS/FEM module and the comfort access system. These codes will help pinpoint whether the issue is with a specific antenna, a door handle, or the central control module. Repair often involves replacing the faulty component and potentially coding it to the vehicle.

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