quoris

I am hoping that someone has had this happen before and that it will be an easy fix. So i was out and about and got back into the car go to start it and car says "press break pedal". ???? I thought i did. press harder on the break pedal and same thing then it also says air suspension failure. Well maybe i just hoped in and tried to start it to fast so i take out the key open the door, close the door put key in, turn on, press pedal and try to start but same thing. So i think i will need a tow. then after a number of random tries it just starts. ???? ok maybe a fluke. a few weeks later same thing and now it is stuck in the driveway. any ideas?

deilenberger

I'd suggest you become familiar with our DIY subforum..

Specifically: https://rennlist.com/forums/cayenne-diy-224/

PS: It's "brake" pedal. Just sayin..

quoris

I forgot to mention it dose say on the dash brake proportioning failure for a brief second.

Wisconsin Joe

Betcha a buck that you have water under the driver's side carpet.

And that the stupid 'crimp the conductors together and wrap them with tape" connections have corroded and failed.

I had the exact same symptoms.

Same warnings on dash, same 'worked after a number of tries, worked fine for a while, until it didn't', same everything.

The DIY forum deilenberger pointed you to has this thread:

https://rennlist.com/forums/cayenne-...-moisture.html

It's a bit of a pain to get under the carpet (you need a specific socket to unbolt the seat), it's awkward propping it up to get under it, it takes forever to properly dry out the foam underneath (three days in my case), but the actual repair of the wires is just basic wiring.

quoris

Thank you I did look in the dyi but did not know this water thing was it. I will tear it out and take a look. I will get back to you all and report back. It feels dry but it don't mean much. i need to put eyes on it to be sure seeing how it sounds like a not IF but WHEN problem.

Wisconsin Joe

The top of the carpet can be bone dry, while the foam underneath is saturated (as in dripping saturated).

In my case, I had a big 'snow blob' on the windshield that blocked the drains and a bunch of water came in through the HVAC.

My carpet was quite wet (both sides) and I put a space heater & small fan in to dry them out.
A day or so later, it seemed to have dried out completely.

4 or 5 months later, the car pulled the 'no start', as described in your OP.
Pulled the carpets up and was able to wring a considerable amount of water out.

I don't know if I'd call it a 'when' issue. But if you get water in the interior, it's pretty easy to have happen.

jeff spahn

I am now seeing that keeping this vehicle in a garage is the best thing for it. Never have had any water inside and now I know I don't!!!

Wisconsin Joe

Not all of us are able to do that.

quoris

well I took have been driving it to get more info on it. It never has left me stranded but some time it can take 2-4 min and several attempts to start it. but it seems to always start. when i put the key in all is fine, but when you turn the key to the on position and the drive selector has all gears selected then i know it will not start. pull key out and try again. after doing this for 20sec- 4min all of sudden every thing works fine. after resetting the trouble codes the only one that is constant is the "1299 gateway and fault is currently active". It acts like it has not woke up yet and wants to sleep in. like it is not initializing all of the sub systems and when the signal finally goes threw everything wakes up and is fine. here is a video if it. I have checked under the passenger and driver side carpet and found no moisture the wires look brand new on both sides. replaced the battery as well but made no difference.

deilenberger

quoris, have you owned it from new? I see it has about 126,000 miles on it. If you aren't the original owner - it's entirely possible (indeed likely) that at some point in it's prior history the footwells in the front did become bathtubs. The wire corrosion unless fixed will eventually get worse, even if the interior is not particularly damp. Just use of the truck will cause vibration that will eventually cause the junctions to fail.

As they say in the financial world "Past performance is no indication of future performance.." - I'd be pulling the carpeting up and unwrapping the wiring harnesses, or looking for someone who could accomplish that job.

I think your course of action at this point is - either continue driving it until it absolutely refuses to start (or stops running while driving it - which could be interesting) and deal with that outcome, or actually do a bit of work and take a look at the junctions (right down to pulling the protective tape off each junction and examining it) - then repairing as needed and sealing up with a waterproof junction cover. That process is very well described in our DIY area. Enough people have experienced exactly the same symptoms you are - and this has been the cause that it's not a WAG sort of diagnosis.

Or you can ignore everyone.

Your choice at this point.

You previously said: What changed?

quoris

i did pull the carpet on both sides and it is dry and looks brand new from the factory. i took the wiring loom apart but found no splice. all looks good. ran great last summer when i bought it but as the weather turned so did the car.

deilenberger

I can promise you there ARE splices in the harness. They may not be obvious - but they're there. On the drivers side - some people have even found splices on the part of the harness that goes up the inside of the firewall (under the dead-pedal.)

dorumac

quoris

everything looks new under the carpet

all are shiny bright copper

deilenberger

That side looks good - how about the other side?