I’m getting weird signals with a multimeter (only showing 1.6v on the 12v pin) so I plugged in a curt 7-way plug tester/emulator, and it is indicating 12v power. So either I’m an idiot that can’t use a multimeter (likely) or the 12v light on the tester doesn’t really need 12v to light up. Anyway, the tester works just fine for all functions except brakes. When you press the brake pedal the brake indicator on the tester does NOT light up however the turn signal indicators go steady on. They flash as expected when you actually use the turn signals.

I guess I can see the turn signal indicators working like that as being correct, if the trailer only has two lights on the back. But surely there should be power going to the brake pin as well, right? Is this a wiring problem or a car programming problem? 958 Cayenne S with factory trailer option that I don’t think has ever been used.

 

It's possible the Curt tester is just indicating there is a signal (some voltage) and not actually confirming it is 12 volts. Recheck with the multimeter and make sure you have a good ground connection.

Do you have a brake controller installed? That is necessary to output a brake control voltage at the connector.

 

Ah! Duh. No, I don’t yet. I was testing the outlet before I installed anything to make sure it was working correctly, didn’t realize you get zero voltage on the brake wire without a controller, I thought it would be something but not nothing.

still concerned about the voltage though. I’ll re-test but I’m pretty confident that I’m doing it correctly. It’s probably worth just heading over to the dealer and having a tech take a look. It’s either working correctly or it’s not, worth an hour of labor to be sure.

 

How old is the connector? Had similar symptoms on mine last year. No evidence of issues on the outside of the plug. Pulled it apart. Inside was totally corroded. Some of the wires fell apart when we pulled off the sleeve. Replaced it and issue have resolved.

 

original blank plate was over the connector before I installed the 7-way plug so I’m guessing it’s original and never used. Car is a 2017

 

The voltage for the brakes is variable. On the old stand alone units u can turn up the gain to simulate a heavy brake load and light up a tester. In newer integraded systems the computer is modulating voltage. While the car is stopped and the brake is applied the car knows it doesnt need much so its probably working fine.

 

Had a tech take a look, he told me it was working fine. Hooked up the PWIS and showed me how the car turns off voltage to the plug if there’s nothing connected, and then plugged in my Curt tester and it immediately turned on. Can’t remember the name of the parameter but it definitely went from off to on when we plugged it in. So apparently seeing really low voltage with a multimeter is normal if there’s nothing connected to it.

edit: as an aside, if anybody is in Northern VA the new Porsche Chantilly dealership has a sick garage and a great waiting area that overlooks the shop. I guess that’s the thing for all the new dealerships they’ve been building.