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No Brake Lights on trailer after factory tow package install


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I just finished installing a factory tow package on my 2009 Cayenne.  When I hook up to a trailer and test, everything works except for brake lights.  I checked for power at pins 3&9 on the 7-pin and only have power present there with blinker and not brakes.  I've check all fuses related to the tow package (1,3,5,19,&41) and all are good.  I tested the trailer on another vehicle and the brake lights work.  Since I don't have power to those pins, the issue has to be with the Cayenne.  Do I need to have the computer flashed if I am not using electric brakes?  The trailer I will be hooking up to has surge brakes, so I didn't think I needed to visit the dealer.

Any assist would be greatly appreciated!!!

Not sure if it makes a difference, but when I purchased this car, it had a Curt hitch with a flat blade connector in the back compartment.  I didn't trace out and remove this wiring, only the hitch.

Thanks

-Ty

Edited by TyS
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5 hours ago, TyS said:

I just finished installing a factory tow package on my 2009 Cayenne.  When I hook up to a trailer and test, everything works except for brake lights.  I checked for power at pins 3&9 on the 7-pin and only have power present there with blinker and not brakes.  I've check all fuses related to the tow package (1,3,5,19,&41) and all are good.  I tested the trailer on another vehicle and the brake lights work.  Since I don't have power to those pins, the issue has to be with the Cayenne.  Do I need to have the computer flashed if I am not using electric brakes?  The trailer I will be hooking up to has surge brakes, so I didn't think I needed to visit the dealer.

Any assist would be greatly appreciated!!!

Not sure if it makes a difference, but when I purchased this car, it had a Curt hitch with a flat blade connector in the back compartment.  I didn't trace out and remove this wiring, only the hitch.

Thanks

-Ty

The cayenne was renowned for having a faulty rear comfort control module which would not work properly with factory Tow package. Problem resolved by replacement and coding of new module which is by PIWIS unfortunately, note even the dealers sometimes could not get the pesky thing to work properly. Good luck. 

 

https://www.etrailer.com/question-165474.html

 

This thread was very interesting and also if you see they had issue with brake lights not working and bought a kit from Porsche to fix it! 

 

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Might not be relevant in this case, but I found that if you use a coupling adapter (like a 7 to 4 pin) that has built in LEDs to “test” the lights are functioning it screws up something on the Cayenne side of things and generates weird behaviors and errors (on mine anyways). The test lights are basically useless anyway, because they don’t work properly unless the trailer is attached - so why not just look at the trailer lights...

 

So if your kit (or the left over Curt hitch) for some reason has indicator LEDs it might cause problems. But if it doesn’t probably not.

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8 hours ago, lewisweller said:

The cayenne was renowned for having a faulty rear comfort control module which would not work properly with factory Tow package. Problem resolved by replacement and coding of new module which is by PIWIS unfortunately, note even the dealers sometimes could not get the pesky thing to work properly. Good luck. 

 

https://www.etrailer.com/question-165474.html

 

This thread was very interesting and also if you see they had issue with brake lights not working and bought a kit from Porsche to fix it! 

 

I'm hoping that the module isn't faulty.  I read your attached thread and it made mention of needing programming/activation if you have PASM, which it does.  Some owners reported that they didn't need any programming for the lights to work, but I wonder if they didn't have air ride.  This is my 1st Porsche (20yrs Audi) and I haven't been to a dealer in at least 17 years.  I was able to program keys, recode features, etc.  I've come to learn that Porsche doesn't offer the same tool to owners at least not without big $$$.  

Since my tow kit is 100% factory, I'm hoping the dealer will just be able to program it with PIWIS.  Thanks for the info...now off to the dealer.

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7 hours ago, Zakowsky said:

Might not be relevant in this case, but I found that if you use a coupling adapter (like a 7 to 4 pin) that has built in LEDs to “test” the lights are functioning it screws up something on the Cayenne side of things and generates weird behaviors and errors (on mine anyways). The test lights are basically useless anyway, because they don’t work properly unless the trailer is attached - so why not just look at the trailer lights...

 

So if your kit (or the left over Curt hitch) for some reason has indicator LEDs it might cause problems. But if it doesn’t probably not.

Funny...I do have that adapter (Reese) with LED.  Since I had no brake lights, I removed the adapter and tested voltage at the tow hitch plug.  Since it didn't work there, it ruled out the trailer and plug adapter.  But based on what you say, after I get this working I will probably pick up a different adapter to avoid any further issues.  I agree on the test LED...Thanks!

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  • 3 weeks later...

Just wanted to give an update on the trailer brake issue...  I brought the Cayenne to the local Porsche Dealership to have the brake module recoded and that fixed the issue.  The cost was $200 to have the module recoded, but I didn't have any other options.  A lot of owners were lucky and the module worked fine out of the box, but in my case everything worked except the trailer brake lights.  I just ordered a Durametric cable in hopes to avoid future trips to the dealership.  Thanks to all for the assist!

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