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2019 Golf R - Key Fob Not Detected / Immobilizer Active

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Chris P. · rep 0 · May 25, 3:21 AM · 1 replies · solved · Question

Vehicle: 2019 Volkswagen Golf R

Hey VW community, I've got a weird problem with my 2019 Golf R. Sometimes, when I try to start the car (it's a push-button start), I get a message on the dash saying "Key Fob Not Detected" or "Immobilizer Active." It usually happens after the car has been sitting for a few hours, and it's completely random.

I've tried replacing the battery in both of my key fobs, but the issue still pops up. Sometimes, if I hold the key fob right up to the steering column, it'll start, but not always. It's really frustrating and makes me nervous about getting stranded. The car starts perfectly fine most of the time, then out of nowhere, this happens.

Is this a common problem with the Golf R or other newer VWs? Could it be something with the car's antenna for the key fob, or maybe the immobilizer module itself? Any advice on what to check would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:21 AM

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ClearTheCode admin answer:

Experiencing "Key Fob Not Detected" or "Immobilizer Active" messages on your 2019 Golf R is a significant inconvenience and points to a communication issue within your vehicle's access and start authorization system. Here's a breakdown:

Potential Causes:

  1. Weak Key Fob Battery (already checked): While you've replaced them, ensure you used high-quality, fresh CR2032 batteries. Even new batteries can sometimes be weak.
  2. Interference: External radio frequency interference (from other devices, cell towers, or even smart home devices if parked in a garage) can temporarily block the key fob's signal.
  3. Vehicle's Key Antenna/Receiver: Your Golf R has multiple antennas that detect the key fob's presence. If one of these antennas (e.g., in the center console, trunk, or near the steering column) is faulty, damaged, or has a loose connection, it can lead to intermittent detection issues.
  4. Comfort Control Module (BCM/J519): This module manages many electrical functions, including keyless access and immobilizer functions. A fault within this module can cause communication problems.
  5. Immobilizer Module Fault: The immobilizer system is designed to prevent unauthorized starting. A fault in this module or its communication with the engine control unit (ECU) can trigger the "Immobilizer Active" message.
  6. Wiring Issues: Damaged or corroded wiring between the key antennas, comfort module, and immobilizer components can cause intermittent failures.

Troubleshooting Steps:

  1. Test with Both Fobs: You've done this, but confirm both fobs exhibit the same behavior. If only one acts up, the issue is likely with that specific fob.
  2. Change Parking Location: Try parking your car in a different spot for a few days to rule out external RF interference.
  3. Check for DTCs: A specialized VW diagnostic tool (like VCDS or ODIS) can pull codes from the Comfort System (Module 09), Immobilizer (Module 25), or Central Electronics (Module 46). Look for codes like:
    • B100000 - Electronic immobilizer active
    • B100100 - Key not recognized
    • B100211 - Antenna for access and start authorization - Short to ground
    • B100215 - Antenna for access and start authorization - Open circuit/short to B+
  4. Proximity Test: When the issue occurs, try holding the key fob in different locations inside the car (e.g., cupholder, passenger seat, near the rear view mirror) to see if it helps, which might indicate a weak spot in the antenna coverage.

When to See a Shop:

  • If the problem persists after trying new batteries and ruling out external interference.
  • If you're unable to start the car consistently, as this is a safety and convenience concern.
  • If diagnostic scans reveal specific fault codes related to the key antennas, comfort module, or immobilizer. These components often require specialized tools for diagnosis and replacement/reprogramming by a VW technician.
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