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Troubleshooting Stop/Turn Signals Not Functioning on a 2005 Porsche Cayenne with LED Trailer Lights


2005 porsche cayenne S Trailer lights question. I have the setup already to receive a 7 pin adapter. My trailer has a 4, so I bought a generic 7 to 4 pin adapter. I have seen so many forums about this LED lighting issue. Im not sure if this applies to me or not... My running lights all work fine when trailer is plugged in. However I have no brake lights and no turn signals on the trailer, despite working running lights. I tried the trailer plugged into my fathers yukon denali and it worked perfectly with running lights, brake lights and turn signals, using the same adapter as I was using to the cayenne. Will the etrailer 7 to 4 pin adapter solve my problem?

Expert Reply:

First thing you want to do is test the 7-way on your 2005 Porsche Cayenne with a circuit tester like our part # PTW2993 to determine if the lighting functions are working correctly on the connector. See the attached picture to see what pin carries which circuit. You will want to have a buddy apply the different taillight functions of your Cayenne and then using the circuit tester check the appropriate pin for voltage. If this check out then you know the vehicle wiring is not the problem.

Have you tested the trailer to see if the problem could be there? You might try a different vehicle with a working 4-way to see if it will illuminate the stop/turn signals of the trailer. If not, check the wiring and connector for shorts and fix as necessary as well as check the grounds of the taillights.

If the wiring of your trailer and tow vehicle check out the # TR20141 would be the correct adapter for you vehicle that should fix the problem you are experiencing.

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expert reply by:
Jameson C

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