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Papagut

Critical electrical system fault(s)

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@jagman1 thanks im gonna check that relay later today hopefully that's my problem wish me Luck 😁👍✌️ Any part numbers for that relay by any chance ?

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Part number: 955 615 027 00

Tapping on my relay box would clear the errors temporarily. This relay powers the CAN network's switched power to the many ecu's in the car.

Edited by jagman1
  • Upvote 1

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Yo Jagman thanks for the advise, mine have good wiring on it and needed the relay replacement to correct the error! I did replace with PN you mentioned. For the others that would be needing it, the relay is marked with a distinctive "433" on top of it and has a Audi/VW PN 3D0 951 253 A on it.

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Yea, it's one of those items that are almost twice the price from VW/Audi than buying it from Porsche. Funny how that happens sometimes, strange pricing.

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You bet! I'm glad it worked out. I spent 20 hours trying to figure that out. Hopefully it saved you some time.

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Had the same problems. Been driving me crazy for few days now. Thank you you guys for an awesome pointers. Would get working on the situation tomorrow.

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I have 2 ctt,s so I can swap bits to test faults. One of them for the last 6 months has been giving the same psm, abs and big red brake proportioning sign, my loom is dry, I've swapped the 433 relay by the battery, batteries fine, has 2 garages plug in obd11 ,they can't access it. Has anyone found anything else to cause this?

General things to note, I just done the valley pipes and y pieces at the back of the motor,was still ok then but then the expansion radiator bottle split so replaced that, and had welding done on rear exhaust, . Then this problem showed.

I think coincidence, and is something else?

Also there's a mobridge on the stereo and a Denison blue tooth in there too, could it be them?

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I new to this forum also so I maybe repeating things that have been previously covered.

My 2004 cayenne S is experiencing a lot of these symptoms also plus a few more, speedometer does not work when I have the brake portioning error.

I have had the brake proportioning error on and off for some time, its happening more often now. We had not driven the car for over a week and the error came back virtually on most of the time.

I have had the car since new and I have never changed the battery but I have had no reason to change as it starts first time every time with no issues.

I read that this could be a possible cause, what is your opinion on this?

I have pulled back the carpet and checked the first set of wires that were connected with electrical tape they were fine, my floor is completely dry

Your help with this would be appreciated.

 

Thanks

 

Alan

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You must let us all into the secret as to how you have managed to make a battery (Moll?) last for 14 years (-:

 

I'd change it/them.

 

 

 

 

 

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Changed the battery but the error is still there. Back to finding the corroded wires I guess.

But before I do that I will change the relay that was discussed earlier?

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Have you checked that your alternator is putting out 14.4v or thereabouts?

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I have a development to share: after nearly 10 years, this same set of symptoms suddenly returned for me: brake proportioning, PSM, ABS, speedometer - all offline + can't put it into gear. I went straight to the same place that caused me trouble all that time ago: drivers side, under the carpet, right about where the footrest is, and exposed the wiring harness. Of all the reconnections and cleaning up that it did - there it was: one small power line had become corroded and broke loose. Cleaned and reconnected, all systems immediately back up. I'm not saying that there are not other causes for this trouble, but only posting this in the hopes that I can help another member out. 

 

Here is a post-repair picture, the red lines you see looping back upward in the centre of the image - those were my culprit. The thinnest of them had come loose.  

 

Hope that this may help someone out. 

IMG_1753.JPG

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Before you go to a lot of trouble, hook up jumper cables from another automobile or charge the battery overnight and see if the extra boost allows some of the systems to come back online. If they do, then you know for sure it's your battery. Replace it. This is a common problem with the Cayenne. The battery has to be at its highest performance or this auto will let you know it with all kinds of crazy electrical gremlins and error/fault messages. This happens well before the battery is even close to dead. A strong start means nothing. If you have short commutes, hook up a battery charger on the weekend a couple times a month. Otherwise be prepared to purchase a new battery every 2 years or less. 

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Hi Papagut, thank you so much for your hard work and research. I have exactly the same issues on my Cayenne S 2008 car.

Lots of water in the front and back of the car and getting all the same fault messages.

 

Unfortunately my case starts about 100miles away from home, so I had to manually override the P on the gearbox and drove the distance in about 5.5 hours.

I confirm that the car drives in 1st/2nd gear, with all the GPS off and the parking assistance off. My headlights works and I believe also the break lights.

 

After cleaning all the water from the matts and the carpet and the bottom of the car, I am now trying to investigate what is wrong. The first thing I checked was the corrosion of the split wires. I have only looked so far the driver's side and from the 3 splits I found 1 cable (the brown one) like in the photo below. There is no copper at all the two wires not even touching each other. Is it possible that the copper completely eroded and disappeared? OMG how is it possible that Porsche knows about this and they do not make a freaking recall? Poor engineering and definitely poor assembly work by the engineers.

 

Anyways - my question is should I clean up the cable and make a new connection of the brown cable? Is it possible that they were never connected and just sitting there in the black electrical tape?

 

Thank you for your help!

 

Splits.jpg

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4 hours ago, Demetris Nenes said:

Hi Papagut, thank you so much for your hard work and research. I have exactly the same issues on my Cayenne S 2008 car.

Lots of water in the front and back of the car and getting all the same fault messages.

 

Unfortunately my case starts about 100miles away from home, so I had to manually override the P on the gearbox and drove the distance in about 5.5 hours.

I confirm that the car drives in 1st/2nd gear, with all the GPS off and the parking assistance off. My headlights works and I believe also the break lights.

 

After cleaning all the water from the matts and the carpet and the bottom of the car, I am now trying to investigate what is wrong. The first thing I checked was the corrosion of the split wires. I have only looked so far the driver's side and from the 3 splits I found 1 cable (the brown one) like in the photo below. There is no copper at all the two wires not even touching each other. Is it possible that the copper completely eroded and disappeared? OMG how is it possible that Porsche knows about this and they do not make a freaking recall? Poor engineering and definitely poor assembly work by the engineers.

 

Anyways - my question is should I clean up the cable and make a new connection of the brown cable? Is it possible that they were never connected and just sitting there in the black electrical tape?

 

Thank you for your help!

 

Splits.jpg

 

Porsche does not use black plastic tape.

Solid brown wires are usually grounds. Perhaps a third party radio installation?

 

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Thank you Loren, the radio is still the original, but I did have iPhone interface installed on the car, so maybe it is something they did.

I have three wires that are covered with black electrical tape. If it is a ground cable can it be the cause of the faulty messages described above (key ignition faulty, break proportioning and chassis failure?

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In my opinion you have absolutely found the source of your troubles. The symptoms were the same, and your picture may as well have been one I took myself. There were no wires in my harness that were left with an intentional dead ends, and I can even remember that particular wire being in a similar state. Mine had corroded away entirely just like the wires you are holding. I remember both times the wires terminated in a larger connection in my car, but mine is a 2004, so potentially different. Were these two lines the only two inside some tape that you have cleared away? If they were clearly the only two inside the tape - then most definitely, clean them up and reconnect them. I would be willing to bet that your systems will all come back up. 

 

If you found them just like the image, naked and loose inside the bundle of wires, then I would be careful to search for their original near connection points. It is a little harder to see in your image, but behind your finger looks like a connection for a number of larger wires wrapped in electrical tape? I would inspect that too while you are in there. 

 

Another thing: right behind your thumb on the left on the thinner of the two wires looks like more corrosion maybe? Watch out for that, you may reconnect everything perfectly but there may be more corrosion further up the line just waiting to cause more trouble. When I was doing mine I just felt the flexibility of the wire for any signs. 

 

So, 100% I think you have the problem right there inbetween your fingers, just be careful that you reconnect them back the way they were originally, then afterward get the wheel wells off and clean out the drain points that tend to clog up and cause water to get into that area. Write me back if you want more info on that and good luck! 

 

Mark

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6 minutes ago, Papagut said:

In my opinion you have absolutely found the source of your troubles. The symptoms were the same, and your picture may as well have been one I took myself. There were no wires in my harness that were left with an intentional dead ends, and I can even remember that particular wire being in a similar state. Mine had corroded away entirely just like the wires you are holding. I remember both times the wires terminated in a larger connection in my car, but mine is a 2004, so potentially different. Were these two lines the only two inside some tape that you have cleared away? If they were clearly the only two inside the tape - then most definitely, clean them up and reconnect them. I would be willing to bet that your systems will all come back up. 

 

If you found them just like the image, naked and loose inside the bundle of wires, then I would be careful to search for their original near connection points. It is a little harder to see in your image, but behind your finger looks like a connection for a number of larger wires wrapped in electrical tape? I would inspect that too while you are in there. 

 

Another thing: right behind your thumb on the left on the thinner of the two wires looks like more corrosion maybe? Watch out for that, you may reconnect everything perfectly but there may be more corrosion further up the line just waiting to cause more trouble. When I was doing mine I just felt the flexibility of the wire for any signs. 

 

So, 100% I think you have the problem right there inbetween your fingers, just be careful that you reconnect them back the way they were originally, then afterward get the wheel wells off and clean out the drain points that tend to clog up and cause water to get into that area. Write me back if you want more info on that and good luck! 

 

Mark

Thank you so much Mark! I will take photos of the other wires as well and post them here. There is no rush to fix it and just want to do the right thing. Knowing me, in the end I will just take the car to the Porsche dealer to take care of it (as I always do!), but at least it will save me a $$$ to point them in the right direction.

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Mark - you were right! I felt brave this morning, took off the battery and cleaned up the cable and put it together again. The break proportioning and the key ignition faulty alerts went away, but still have the chassis error and a headlamp faulty message. The headlamp could be from a weak battery ( I have been using the battery a lot without driving the car).

Needless to say I will check all the connections on the driver's seat and the front passenger seat to see if anything else is loose. Also the back floor is wet - so wondering if there are any split wires there as well.

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Great news! In my cayenne, I found wiring in both sides that was corroded, but only those wires that you were holding were corroded completely and causing my major problems. Nothing found in the back for me, and no moisture traveled that far, just drivers and passengers side front. Perhaps some of the other errors you are seeing are persistent and you just need the faults to be cleared? You may just need to drive it around a bit. 

 

I'll pass along one more related tip that has helped me out quite a bit for my electrical issues: under the carpet in front of the drivers side seat is where the battery grounds to the frame. If you are getting some moisture in the footwell carpeting, I would inspect that too for any corrosion and clean it up for a nice connection. I put some conductive grease on mine. I do that once a year or so where I am because we have wet snowy winters and use salt on the roads and that main connection is right about where your wet feet go.

 

Glad to hear you have it mostly sorted out. Good luck, 

 

Mark

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