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955/957/958 Cayenne DIY: Wiring problems due to moisture


955/957/958 Cayenne DIY: Wiring problems due to moisture

Old 10-29-2016, 08:11 PM
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Default 955/957/958 Cayenne DIY: Wiring problems due to moisture

Are you getting all these errors when you try to start the car? Press Brake Pedal, and you pressed it? Tired of searching the internet, and being told it is just the wires in the drivers side failed, but no details?

Looks like a Christmas tree on the dash?

Ignition Lock Failure, Brake proportioning Warning, ABS light, Traction Control, Check Engine, Brake Light Flashing. Stuck in Park May or May not start.

I had water leaking in from the door to body grommet/hose. If your carpet is wet or damp, this is most likely the result of a small leak for a long time.

One person mention that relay 443 on top of the battery may be the culprit if you don't have a water problem.

So you have got all these on at once, car may or may not start. If you can get it to start, you are not stuck, but are in a limp mode. You can also put it in neutral for a tow.

You can remove the dual Allen wrench under the rubber mat in the bottom cubby.

Remove the two Allen screws, that you can see from that cubby towards the front of the car. Lift the center console surround, it snaps out from the back towards the front, with the front slotted in under the ash tray.

With a long tool, look in front of the shifter, you will see in my case, a 2009 Cayenne a red arm that moves the lock, press it gently to the left and you can now shift out of park.

WARNING: Your brake lights will not work and you can not leave 2nd (I think, gear) if you drive the car this way. I am not sure what else may not work from a lighting perspective.

Now if you want to fix it:

First, pull out the drivers and rear passenger mats if you have them on the Driver's side.

Behind the drivers seat, slide out the plastic beauty covers of the left and right rails.

Remove the two plastic covers, just in front of the Drivers seat base, and with a 5 point bit, remove both the screws that hold the seat in place. If you are having trouble with this, it is the same procedure to get at the battery.

Next, slide the seat all the way back, and then tilt the seat back forward.

Now, push the seat head rest with your hand back, the seat should now pivot on the rear hinges and tilt back.

Slide the forward with the power switch, and the seat will move out of your way even more. You can reverse all this later when you put the seat back, this method just avoids hitting the steering wheel.

Now, you do not need to open the battery box, just remove the nut from the ground cable, next to the seat bolt for the transmission tunnel, get a back and wrap it around the end of the cable, I used a rubber band for good measure. This will keep you from accidentally applying power.

Now the only hard part, you need to pry up the carpet, and it is a little tricky because we will not be removed the door sill.

Start from the B pillar, under the door sill, this will give you some flex in the carpet, when you try to remove the dead pedal section of the carpet.

Once you have it out from under the door sill, you can prop it up, I used a 32oz plastic cup.

Now is a good time to dry any water, etc from under there. My car would still start, so I ran the car on idle, high heat, full re-circ, and floor only for 3 hours.

Now we can open the flat plastic wire protector. Just release the tabs with a small screw driver, then fold it back, towards the door. You again may find tape, or a weight of some sort to hold it open.

So the cloth is multi layer and I assume was at some point sticky on the bundle. You can unwrap the end, right where it enters the flat black wire protector. That lets you peel back several strips of cloth that run parallel with the wires. Another pieces is wrapped around the wires circularly, no need to disturb that.

You will find 3 pairs of wires, in my case one was crimped and had a plastic protector. 2 were connected somehow, with cloth electric tape wrapped around the twisted pairs. One just pulled off and I had plastic wire stubs, the inside was corroded to copper dust!

Note the green copper wire, about 2 inches of it, turned to dust in the electrical wrap!

The other looked fine.

So the problem is two fold, 1 they are lousy connections, 2, they sit at the bottom of the bundle, right where water would pool and absorb into the black wrap. You could see the corrosion on the black wrap in my case, so I had a pretty good idea, plus when the car was on and I pressed that spot, more alarm dings flashed!

I pulled all three pairs of the crimped wires, and moved them further up in the bundle, under the dead petal, so I could get slack and re-locate them later.

The bad red wires I striped back 1 inch, clipped the corrosion off, butt joined and soldered them with shrink tube, then folded over and wrapped in electrical tape.

The good black wire, I still pulled the electrical tape, shrink tubed it, folded over the remaining shrink tube, and electrical taped it, with zip tie to hold the tape down.

Finally I tucked all 3 wires on the top of the bundle, under the factory zip tie behind the dead pedal, and zip tied them to the bundle. This way if water gets in I have to have 4 or 5 inches of water for it to sit there for a long time and repeat what happened.

I was able to nicely put the fabric electrical tape together, zip tie it in several places, and tuck it all back in.

Pushed the carpet back in, connected the battery, car started no problem few errors, but all cleared except the check engine light after a short drive and putting my seat back in.

This really should be a recall.

Took me about 1.5 - 2 hours to complete.

Last edited by deilenberger; 04-09-2018 at 02:29 PM.
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Old 08-24-2017, 06:24 PM
Kris Murphy
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Default 955/957/958 DIY: Wiring problems due to moisture

I was just reading a thread about the wiring that gets wet in the footwells that cause all sorts of electrical, car not moving issues. I remember when it happened to me that I could not find any photos of the exact locations.

Possibly they are here, but search hates me, so I took some photos and decided I was going to post them. That was two years ago. Reading the thread reminded me that I took the photos, so I am finally posting them.

The pictures below are from the drivers side, but I believe the passenger side is the same location. Why Porsche felt the need to splice wires, I have no clue (I assume it has something to do with options). Why they decided to have the splices in an area that could get wet, and did not do enough to protect the, I really don't know.

Here is what the wires look like when found. Notice the black fabric tape. Those are the splices.

Here is how I fixed them. Soldered, lots of tape around the splice. Then some of that press and seal wrap I stole from my wife, then more tape, then some wire ties.

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Old 04-09-2018, 02:13 PM
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Default 955/957/958 DIY: Wiring problems due to moisture

It seems very common with ALL series of the Cayenne to have footwell floods in the drivers and passengers footwells. If this happens often enough, or if the water hangs around under the carpeting long enough - damage will occur to a wiring harness bundle that runs in each footwell. Porsche in their infinite wisdom for some reason decided that it was a good idea(tm) to have electrical splices in the cable bundles - located in an area where they are going to (sooner or later) get wet. And the splices they make were not waterproof. The results of electricity and water and copper wiring is copper oxide - which unfortunately doesn't conduct electricity. Many of the failures seem to have the effect of random, odd, multiple electrical failures in a variety of Cayenne systems. Windows don't work, brake lights are always on, or never on, even the steering column may not unlock.

The fix is - pull up the carpeting, dry out the area and then fix the splices in the wiring bundles. And this means checking BOTH footwells - there are wiring bundles with splices in both.

There is info scattered around on how to do all this - but I thought I'd bring together some good photos and writeups members have contributed - in a single thread so you have an idea of what you're facing - all in one DIY writeup.

Thanks to Kris Murphy and Tourag for the wonderful photos and posts! If anyone stumbles across other writeups that should be part of this thread - please send me a PM with the URL of the posting.

Last edited by deilenberger; 04-09-2018 at 02:37 PM.
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Old 09-02-2018, 02:11 PM
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I'm adding the following from Shawn - it popped up in the normal forum in a discussion on the wiring - and looks ideal for fixing these harnesses:

Originally Posted by Shawn Stanford View Post
I've been seeing these popping up on FB ads: https://www.amazon.com/Wirefy-Solder...55545899&psc=1
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