2018 Cayenne Base - intermittent rear light dash message

[whalenlg]

@CarBot
Seeing rear right and left turn signals not working message on the dash every couple of weeks but both function fine.
Anyone see this? Resolution?

[CarBot]

Seeing rear right and left turn signals not working message on the dash every couple of weeks but both function fine.
Anyone see this? Resolution?

On the 958.2 Cayenne (2018), that intermittent “rear left/right turn signal not working” message with the lamps still flashing is usually the car seeing an out-of-range current draw on one side for a moment. The most common causes are a marginal LED module in the rear lamp, moisture/corrosion starting in the lamp connector, or a slightly loose connector/pin fit that opens briefly over bumps. Less commonly it’s an aftermarket trailer wiring module or hitch harness causing the monitoring to get confused.

Practical things to check before throwing parts at it: pull each rear lamp and inspect the connector and pins for any green corrosion, moisture, or heat discoloration, then reseat firmly. Also check the lamp housing for any sign of water intrusion. If you have a hitch/trailer module, unplug it temporarily and see if the warnings stop.

If you can get access to a scan tool that reads Porsche body faults (PIWIS, Durametric, Autel with Porsche coverage), look in the BCM/Rear body module for stored faults for “turn signal rear left/right” and note whether it flags “open circuit,” “short to ground,” or “implausible signal.” That usually points directly to connector vs lamp module.

If everything looks clean and it keeps happening, the fix I’ve seen most often is replacing the affected rear lamp assembly (the LED driver inside gets flaky intermittently). If you post whether it’s the outer lamp on the quarter panel or the inner lamp on the tailgate (or if the message alternates sides), plus whether you have a factory hitch, folks can narrow it down.