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2018 Cayenne S - Intermittent "Key Not Detected" Warning

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Kevin B. · rep 0 · May 22, 6:45 AM · 1 replies · solved · Question

Vehicle: 2018 Porsche Cayenne S

Hey everyone,

I'm having a really frustrating issue with my 2018 Porsche Cayenne S. Lately, I've been getting an intermittent 'Key Not Detected' warning message on the dash. It happens randomly – sometimes when I try to start the car, sometimes while driving, and sometimes when I just get in.

I've already replaced the battery in my key fob twice, just to be sure, and it hasn't made any difference. When the warning appears, sometimes the car won't start at all, or the ignition won't fully engage. It usually resolves itself after a few tries, or if I lock and unlock the car a couple of times, but it's becoming more frequent and unreliable.

Has anyone else experienced this with their Cayenne or other Porsche models? I'm worried it might be something more serious than just the key fob itself. Any ideas on what could be causing this electrical glitch?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 6:45 AM

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ClearTheCode admin answer:

The 'Key Not Detected' warning in your 2018 Porsche Cayenne S, especially after replacing the key fob battery, points towards an issue within the vehicle's keyless entry and start system (KESSY) or related electrical components. This system relies on multiple antennas and control modules to communicate with your key fob.

  1. Check Your Spare Key: The first crucial step is to try your spare key fob. If the spare key works flawlessly and doesn't trigger the warning, it strongly suggests an internal fault with your primary key fob, even if the battery is new. If both keys exhibit the same problem, the issue is likely with the vehicle's receiving system.

  2. Scan for Diagnostic Trouble Codes (DTCs): A professional diagnostic scan tool (like Porsche PIWIS or a high-end aftermarket scanner) can read codes from the KESSY module, immobilizer, and comfort access modules. Look for codes related to antenna faults, module communication errors, or key authentication failures. Common codes might include B-series codes related to the immobilizer or KESSY system.

  3. Inspect for Interference: Ensure there are no strong electromagnetic fields or other electronic devices near the vehicle's interior that could be interfering with the key fob's signal. Sometimes, even items like dash cams or radar detectors can cause minor interference.

  4. Antenna and Wiring Inspection: The KESSY system uses multiple antennas located throughout the vehicle (e.g., in the center console, rear cargo area, door handles). These antennas can sometimes have loose connections or damaged wiring. A visual inspection for obvious damage is a good starting point, though internal wiring issues are harder to diagnose without specialized tools.

  5. Module Malfunction: In some cases, the KESSY control unit itself or a related comfort access module might be failing. These modules are complex and require specialized diagnostics and potentially replacement/coding by a Porsche dealership or a qualified independent shop.

When to See a Shop: You should definitely take your Cayenne to a Porsche dealership or a reputable independent European car specialist if:

  • Both your primary and spare key fobs exhibit the same 'Key Not Detected' problem.
  • A diagnostic scan reveals specific DTCs related to the KESSY system, immobilizer, or antenna faults.
  • The issue becomes more frequent, leading to repeated no-start situations.
  • You suspect wiring damage or a module failure, as these require specialized tools and expertise for proper diagnosis and repair. Ignoring this issue could leave you stranded, as the system might eventually fail completely.
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