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On the centre dial of my dash board, when I first start up and drive off, the gear selection shows D and 1 or 2 (depending on temperature).
Once I have been driving for 5 to 10 minutes, the display shows no gear numbers, but PRND are all lit.
Car drives fine and gears change as they should (I can hear the engine note and just feel the changes).
If I stop anywhere, when I then restart the car, it shows gear selection correctly, but again after 5 minutes or so it changes back to no numbers lit and PRDN all lit.
The clock never keeps the time set either, always starts at 1500 when I turn ignition on.
Is this a common problem and if so, where do I need to look at fixing it?
Could it be the centre display or something else?
Last edited by Santacruz; 01-06-2022 at 12:02 PM.
Reason: Added text
It is one of two things to check first. First. take off the wiring harness connectors at the back of the transmission and look at them. If they (on both male and female side) are clean, just re seat them and see if the problem goes away. Spraying them with an electrical contact cleaner won't hurt but wait for it to dry before reconnecting. I also brush Deoxit on the pins and let that dry to improve connection. If they are wet with transmission fluid (most likely cause), your internal oring on the wiring harness has failed or the connector itself has failed and trans fluid is creeping through from the wet side of the transmission to the outside. Clean it off with electrical connector cleaner and order a new internal wiring harness from Roger at 928srus.com. PLus order transmission filter and gasket because you'll be dropping the pan soon to replace that harness. Look at pelican parts website to see how to remove and replace the valvebody on a cayenne because you'll be doing that. It isn't really that hard, just messy. First timer will take about 4 hours. Then also learn how to properly fill your transmission, again on the pelican site. I use Pentosin ATF1 for my transmission but you decide what you want to use.
BTW, if you don't fix this (if the pins are wet) and decide to just let it go, you'll also be buying the harness from the trans to the computer under the driver seat and possibly the computer as the fluid makes its way up the wires and to your transmission computer.
Also, search is your friend. There are several threads on this already in this forum.
I hate it when people post after me with different suggestions but...
I had to think long and hard because I almost completely forgot about this. But I had this exact same problem a few years ago and it was 100% the wiring splices under my carpet (and maybe also a weak battery).
I never followed up to this post that I'm surprised I was able to find, but this issue was resolved after recrimping and insulating the splices under the carpet and replacing my rear battery. Never came back at all.
Thank you thesteve, you picture is exactly what I have. In fact, it could be the same car if it wasn't for mine being grey trim and in kms.
I will check he wiring (I take it, that is under the drivers side (left) carpet).
I have not checked under the carpets yet to see if there is any wetness there, but it is also on my list of todo's to clean and check all the drain ports.
As for the battery, everything else, electrical, seems to function just fine. The car always starts straight away hot or cold, which I believe is from the rear battery.
I have the Bose system, so guess the battery is under the sub.
Also, thank you to jeff spahn, I will make a check of the plugs, while I am not too sure that is the cause, you have made me paranoid enough to check hahahaha.
I did also try searching, before asking for help, but found it very difficult to find anything that resembled my problem. I found the search function difficult as to how to word the search. Various different phrases, revealed no results to match what I was looking for.
Yes, I think it is/was the left side. Don't get carried away by some of the posts involving seat removal and whatnot.
You can do the job with some wire strippers and a crimp tool in a few minutes. The carpet folds up and away by just using your finger tips. -It goes only flush to (not under) the trim.
It's not important, but just so you know (if you even have a rear battery) it only starts the car if you first turn the key counter-clockwise.
Good luck and happy motoring!
Thank you for the reply.
Just as a matter of interest, I am a bit confused.
You say it only starts the car if you first turn it counter clockwise. This is something I know nothing about and don't think I have seen it in my owners manual.
My process at this time is, unlock, open door, out key in ignition, then get in, shut door, put seat belt on, (at this point, if the compressor is running and the suspension is lifting - depending how long I have left car standing - I wait till that has finished. Then I turn the key to the right to start the engine.
When I stop and turn the engine off, I have to then turn the key anti clockwise to unlock key from ignition switch.
So, does that mean I am starting off of the battery under the seat?
I have to check if I have a rear battery, but, I believe for this I have to remove the sub.
I am (if you have not guessed) confused what the 2 batteries are for now. (If I have 2 batteries that is).
Also, I have all the equipment for wiring, so that should not present too much of a problem.
But I also wonder, as I have a fairly good code reader, would there be any codes related to this that i should check for. I haven't as yet done a scan.
In the US, dual batteries are usually only found on 2003 Turbo vehicles and it was offered as a backup way of starting the vehicle in the event the main battery died. I believe it was a standard feature for Turbos in 2003 that Porsche removed as standard for 2004+ model year vehicles. The second battery lives in the trunk, and is only activated by first turning the key counter clockwise before attempting to start. Otherwise the battery simply charges when the vehicle is running and is otherwise unused. There are two subwoofers for the Cayenne. The far more common is a smaller dome shaped subwoofer that fits under a collapsible spare tire. The other is a much larger flat top subwoofer that goes around the rear battery setup. If it looks like there is any possible way a spare tire could fit over the subwoofer, then you don't have the dual battery.
Yup, all good info above. You understood correct about normally only starting with the battery under the seat and only switching to the rear backup batt. by first turning the key CCW.
An easy way to find out your battery situation is from your build sticker. In my case if memory serves it was stuck on the air tank near my subwoofer.
As far as codes, yes. IIRC my main code was related to my PSM not working and the code was something like "PSM system due to a tiptronic loss of communication."
One last thing, there are other splices on the passenger's side and driver's side so you should look for and redo them all. The small signal wires specifically.
There are beefy splices that are "too big to fail" so to speak. YRMV but my other issue solved by fixing splices was an intermittent issue with my self leveling air pump.
My sub is full sized, filling the whole wheel well up. At the front of it, there is a small recess with some tyre goo for punctures.
So if I have 2 batteries, am I understanding this correct?
I start the car the normal way I do, by turning the key clockwise and I assume this uses the battery under the seat.
If I start the car by first turning the key anti clockwise and then as above, then the car starts off of the rear battery.
This is not something that is shown in the owners manual, although there is a section about removing the full size sub to get to the rear battery.
I think I should have a rear battery. but I need to remove the sub and see it to confirm it.
To add:- thesteve, your post appeared as i was making this reply. I have checked my build sheet and yes J2C is one of the options.
I hate when that happens. No problem. So yes. I can't find my digital copy of the owner's manual but yes.
Not sure how long you've owned your 955, but might be worth checking the date code on the second battery.
It's extremely comforting to know it's there, and in fact, during the pandemic with the staying home thing for long stretches, I have used it more than once.
Well, I now have a few checks to make over the next few days.
Once I am done with checks / repairs, I will report back.
The one small thing I hate about forums (whatever they are for) is that they never get edited to solved.
I have spent many hours reading through long lists, only to discover at the end, there was no fix.
I hate it when people post after me with different suggestions but...
I had to think long and hard because I almost completely forgot about this. But I had this exact same problem a few years ago and it was 100% the wiring splices under my carpet (and maybe also a weak battery).
I never followed up to this post that I'm surprised I was able to find, but this issue was resolved after recrimping and insulating the splices under the carpet and replacing my rear battery. Never came back at all.
Well, I have finally got around to checking this wiring, while I am in the process of fitting a new battery.
It looks like my wiring is in perfect condition.
I also checked the carpet and foam and it is completely dry and there are no stains to indicate it has ever been wet.
So, I think I can cross this off of my to do list.
You have to cut the zip ties, dig in there, and remove the black tape on all of the splices, specifically the ones of smaller gauge wires.
Then don't even bother inspecting them, I mean you can.. check for a green tinge.
You have to search and find all of the small gauge wire splices and just redo them.
The damage happens over years, so a smoking gun of detectable moisture is not at all needed. I argue it could happen from humidity alone.
Follow the bundle up the firewall also for at least one hidden splice.
You have to cut the zip ties, dig in there, and remove the black tape on all of the splices, specifically the ones of smaller gauge wires.
Then don't even bother inspecting them, I mean you can.. check for a green tinge.
You have to search and find all of the small gauge wire splices and just redo them.
The damage happens over years, so a smoking gun of detectable moisture is not at all needed. I argue it could happen from humidity alone.
Follow the bundle up the firewall also for at least one hidden splice.
Okay, thanks for the advise.
Time to dig out the solder station and shrink wrap
That sounds good. I just did a quick fix with my favorite tool below and some red butt connectors.
I see they have nice ones for sale now with heat shrinking material built in. I'll be buying some.
01-06-2022, 11:59 AM
Strange gear display
