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2017 Cayenne S - Multiple Warning Lights, PCM Communication Error

0

Mike T. · rep 0 · May 25, 4:48 AM · 1 replies · solved · Question

Vehicle: 2017 Porsche Cayenne S

Hi all,

My 2017 Porsche Cayenne S is having a really strange issue. This morning, when I started it, I got a Christmas tree of warning lights on the dash: PSM failure, chassis system warning, and even a 'faulty engine control' message. The PCM screen also went blank for a bit, then came back on, but it seems to have lost some settings.

I tried restarting the car several times, and sometimes the lights clear, but then they come back. I haven't pulled any specific OBD-II codes yet, but it feels like an electrical or communication issue rather than a mechanical one. The car drives, but I'm hesitant to go far.

Has anyone experienced something similar with their Cayenne? Could this be a dying battery, or something more serious like a failing control module? Any advice on where to start looking?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:48 AM

0

ClearTheCode admin answer:

The 'Christmas tree' of warning lights and PCM communication errors on your 2017 Porsche Cayenne S are classic symptoms of a low voltage condition or a failing battery. Modern Porsches are extremely sensitive to voltage fluctuations, and a weak battery can cause various control modules to malfunction or lose communication, triggering seemingly unrelated fault codes.

Here's what you should investigate:

  1. Battery Health:
    • Voltage Test: Check your battery's voltage with a multimeter. A healthy battery should read around 12.6V when the engine is off. If it's significantly lower (e.g., below 12.0V), it's a strong indicator of a dying battery.
    • Load Test: A simple voltage test might not reveal a battery that's failing under load. Many auto parts stores offer free battery load testing. This is crucial for determining if the battery can deliver sufficient current.
    • Age: If your battery is 4-5 years old or more, it's likely due for replacement, especially if it's the original.
  2. Alternator Output: Once the engine is running, check the charging voltage at the battery terminals. It should be between 13.5V and 14.5V. If it's too low or too high, your alternator might be failing.
  3. Loose/Corroded Battery Terminals: Ensure the battery terminals are clean, tight, and free of corrosion. Poor connections can mimic a failing battery.

When to See a Shop:

If replacing a confirmed bad battery doesn't resolve the issue, or if the problem persists after verifying good battery and charging system health, then a professional diagnostic is necessary. A Porsche specialist can use their PIWIS diagnostic tool to:

  • Read all fault codes from every control module (not just engine codes).
  • Perform a gateway diagnosis to check communication between modules.
  • Identify specific module failures or wiring issues that might be causing the widespread errors. Driving with these warnings can be unsafe, as critical systems like PSM might be compromised.
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