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Key Fob Not Detected - 2017 CT6 Passive Entry Issues

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Mike T. · rep 0 · May 25, 2:53 AM · 1 replies · solved · Question

Vehicle: 2017 Cadillac CT6 Platinum

I'm having a really annoying problem with my 2017 Cadillac CT6 Platinum. The car frequently displays the "Key Fob Not Detected" message on the dash, even when the key fob is clearly inside the car, sometimes even in my hand. This makes it incredibly difficult to start the car, and the passive entry/exit features (unlocking doors by touching the handle, or locking when walking away) are either intermittent or completely non-functional.

I've already replaced the battery in both of my key fobs, thinking that was the obvious culprit, but the problem persists with both fobs. What else could be causing this issue? Is there a sensor or module that commonly fails in these cars?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:53 AM

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ClearTheCode admin answer:

"Key Fob Not Detected" issues on a modern vehicle like your 2017 Cadillac CT6, especially after replacing fob batteries, usually point to a problem with the vehicle's Remote Control Door Lock Receiver (RCDLR) module or related components.

Here are the common culprits and diagnostic steps:

  1. Key Fob Battery Quality: While you've replaced them, ensure you used high-quality, fresh CR2032 batteries. Sometimes, even new batteries can be weak, or cheap ones don't provide consistent voltage.
  2. RCDLR Module Failure: The RCDLR module is the primary component that communicates with your key fobs for passive entry, remote start, and ignition. If this module is faulty, it won't properly detect the fob's signal. This is a relatively common point of failure in some GM vehicles.
    • Common DTCs: A failing RCDLR might trigger 'B' codes (body control module related) such as B3105 (Key Fob Not Detected) or communication codes if it's struggling to communicate with other modules.
  3. RCDLR Antenna Issues: The RCDLR module uses several antennas located throughout the vehicle to triangulate the fob's position (inside/outside). If one or more of these antennas are damaged, disconnected, or faulty, the system can't accurately detect the fob.
  4. Wiring and Connectors: Corrosion, damage, or loose connections in the wiring harness leading to the RCDLR module or its antennas can disrupt communication.
  5. RF Interference: Less common, but strong radio frequency (RF) interference from external sources (e.g., cell towers, power lines, or even other electronic devices inside the car) can sometimes temporarily block the fob's signal.
  6. Fob Programming: Although less likely if it was working previously, a glitch in the fob's programming to the vehicle could cause intermittent issues. Reprogramming might be necessary.

When to See a Shop: Since you've already tried new fob batteries, the next step requires specialized diagnostic equipment. It's highly recommended to take your CT6 to a Cadillac dealership or an automotive electrical specialist. They can:

  • Scan for specific RCDLR module fault codes.
  • Test the RCDLR module's functionality and its associated antennas.
  • Check the wiring integrity to and from the RCDLR.
  • Perform any necessary module reprogramming or replacement. This issue can be a significant inconvenience and security concern, so prompt diagnosis is advisable.
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