AusTexCTT

I'm having an ongoing issue with my 2008 Cayenne Turbo, started on a ski trip last month ( was cold and bit bumpy on som roads but not wet.) this and has continued to happen on and off since that first time.

The problem is my car will throw Chassis control system, Antilock Brakes, Transmission, Oil pressure monitoring system and numerous other error codes. then the dash computer sometimes gets reset and, sometimes goes a little crazy like saying my range to go on the gas I have in my tank is like 2000 miles. Another time it would not show gear position while driving.

Car runs fine a drives fine while this is happening and often a stopping, shutting the car off waiting 1-2 minutes then restarting clears all error, other times not.

CEL light will come on and then clear itself after restarting clears errors and car is driven a bit.

I read that wet wires might cause so I cleaned all drains, and then lifted driver side carpet and dried things using car heater over a few hours and seemed to cure it, then today it started back up again after full day driving with no issues, no water in floor to be found all drains cleared.

I did manage to pull the following code using a basic OBC2 Scanner, ( Durametric is on order now).

Stored Diagnostic Trouble Codes (DTC) (Mode 03)
P1552 - No Description (Manufacturer Controlled Code (Non-Uniform DTC))
Vehicle Area: Powertrain (P)
Area of Vehicle System: -
Controlled by: Manufacturer Controlled Code (Non-Uniform DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
U0103 - Lost Communication With Gear Shift Control Module "A"
Vehicle Area: Network (U)
Area of Vehicle System: Network Electrical
Controlled by: ISO/SAE Controlled Code (Core DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
Pending Diagnostic Trouble Codes (DTC) (Mode 07)
P1552 - No Description (Manufacturer Controlled Code (Non-Uniform DTC))
Vehicle Area: Powertrain (P)
Area of Vehicle System: -
Controlled by: Manufacturer Controlled Code (Non-Uniform DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
U0103 - Lost Communication With Gear Shift Control Module "A"
Vehicle Area: Network (U)
Area of Vehicle System: Network Electrical
Controlled by: ISO/SAE Controlled Code (Core DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
U0121 - Lost Communication With Anti-Lock Brake System (ABS) Control Module
Vehicle Area: Network (U)
Area of Vehicle System: Network Electrical
Controlled by: ISO/SAE Controlled Code (Core DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
U0129 - Lost Communication With Brake System Control Module
Vehicle Area: Network (U)
Area of Vehicle System: Network Electrical
Controlled by: ISO/SAE Controlled Code (Core DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
P1528 - No Description (Manufacturer Controlled Code (Non-Uniform DTC))
Vehicle Area: Powertrain (P)
Area of Vehicle System: -
Controlled by: Manufacturer Controlled Code (Non-Uniform DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
Permanent Diagnostic Trouble Codes (DTC) (Mode 0A)
P1552 - No Description (Manufacturer Controlled Code (Non-Uniform DTC))
Vehicle Area: Powertrain (P)
Area of Vehicle System: -
Controlled by: Manufacturer Controlled Code (Non-Uniform DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
U0103 - Lost Communication With Gear Shift Control Module "A"
Vehicle Area: Network (U)
Area of Vehicle System: Network Electrical
Controlled by: ISO/SAE Controlled Code (Core DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
U0121 - Lost Communication With Anti-Lock Brake System (ABS) Control Module
Vehicle Area: Network (U)
Area of Vehicle System: Network Electrical
Controlled by: ISO/SAE Controlled Code (Core DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
U0129 - Lost Communication With Brake System Control Module
Vehicle Area: Network (U)
Area of Vehicle System: Network Electrical
Controlled by: ISO/SAE Controlled Code (Core DTC)
Controll Unit: $7E8 - CAN-ID ECU #1
P1528 - No Description (Manufacturer Controlled Code (Non-Uniform DTC))
Vehicle Area: Powertrain (P)
Area of Vehicle System: -
Controlled by: Manufacturer Controlled Code (Non-Uniform DTC)
Controll Unit: $7E8 - CAN-ID ECU #1


Any help anyone can give, or advice on where to look for the casue of this gremlin would be awesome.

thanks

-Matt

AusTexCTT

I also have constant, low-level whining that is linked to engine speed up front.

My thoughts were that this probably was either an idler pulley, Alternator, water pump or Power steering pump.

No indicators of issues with steering pump, or water pump, so wondering if this noise is from the alternator could that be leading to low voltage in the battery that might cause a relay ( relay 15?) not to throw when starting? Does not really explain the two times it threw codes while driving, though both of those times I WAS USING THE RADIO.

Was showing 13.0-13-8 volts in software when I took those error readings listed in the previous post, not sure if that's considered low or not on the Cayenne.

deilenberger

Whining in an alternator can be an indication of a bad diode in the rectifier bridge that converts the alternator's AC current to DC current that the car and battery require. If a diode is shorted - AC will go through the diode and be seen on the DC lines in the car. You can try checking this with a voltmeter by putting the voltmeter on "AC" range - say 20V - and seeing if any AC can be measured on one of the power lines in the vehicle (engine running of course.) Another way of checking is with an oscilloscope - again looking across a power feed on the vehicle (and the other scope lead to ground.)

AC noise on a line could cause all sorts of bad things to happen with the multitude of modules in the car. I notice that the majority of error messages you're reading appear to have a root cause of "network" - and certainly AC impressed on the DC would likely cause network problems throughout the vehicle.

13.0-13.8V at idle is pretty much normal - but a shorted diode typically won't effect the output voltage much - it will tend to limit output current which means voltage will drop under a high electrical load (fans, rear-window defogger, etc.)

I would do the AC voltmeter reading first - and let us know what you observe. Ideally - it should read 0.00VAC. Anything much over 0.5V to me would indicate a rather serious problem.

BTW - the reference you may see to relay-15 or "terminal-15" is to the main power lines for the vehicle. Dunno why - but they always have the number 15 associated with them.

Oh - one other possibility - is corroded wiring junctions in the wiring under the passengers seat carpeting. If it had been wet for some period of time - Porsche for some reason would put junctions in wires - I assume when the wire on the spool they were using ran out - they made a junction to the wire on another spool of the same color code wiring and simply continued constructing the harness. Some of these junctions end up going through the big bundle of wiring on the floor pan on the passengers side. If soaked long enough, water is drawn up through the junction into the wire and electrolysis is the result - corrosion of the wire and junction - sometimes a distance up the wire. It may not be immediately obvious - the corrosion may be hiding under the shrink wrap over the junctions. The fix is a new harness (more than the car is worth) - or finding any junction that may have gotten wet and redoing them, with perhaps a length of wire spliced in to replace any which may have corroded. More than one person has had to do this ugly job.

There are shrink-wraps available with a soft meltable inner lining meant to make waterproof joints. I'd suggest any that are done be done using that shrink-wrap. And find the source of the leak and fix it.

RT_955TT_KY

Example photo of wires in the driver's footwell. Notice the multiple splices and dampness.

deilenberger

Yup. Ugly.

What you really need is an old time telephone line-man whose job title was "splicer" - these guys would sit up on a pole for days at a time - splicing together cables with 500 pairs of wire, then waterproofing the entire splice and making it airtight so the cable could be pressurized with nitrogen to keep moisture out.

The 958 series has a nice little trap door built into the carpeting on the passenger (starboard) side that you can open and reach in and feel for any moisture. So far on mine - it's remained dry....

RT_955TT_KY

In full disclosure, that is not a pic of my Cayenne, but one I looked at a couple of weeks ago at a salvage auction. Offered $1k, still waiting to hear back if they accept my offer...04 S

r553

How old is your battery? Funny things happen when the battery is on it's way out. Good luck.

AusTexCTT

Thanks for the replies so far.
I'll be getting out my meter today and testing for AC etc, I'm really leaning towards the alternator being bad as I remembered that my wife had turned her seat heater on yesterday also and that draws a ton of watts, not too long after that the fun began again.


I will be inspecting the wire bundle and cutting out any patches and re-wiring them then properly sealing each and then the whole bundle.

The battery age is unknown as I bought the car about 3 months ago with 120k on it, good service history but no mention of battery replacement.
May just get a new one to be sure.



BTW got a pretty good deal on it at $16,900 at international motor up in Dallas.

I'll be doing the upper and lower A-arms in February and if the alternator end sp being bad I'll do that at the same time.


Since I'm going to be deep into the car next month, would it make sense for me to pick up new idler pulleys, Belt tensioner pulley and S-belt and Water pump and possibly power steering pump and just do those too while I'm in there?

Also planning boost hose gasket refresh throughout, plugs and coils.
Oil change , Transmission oil / filter change, diff / transaxle oil changes.

With 124k on the clock seems like it's about the time when all those things begin to fail, and I don't want to worry bout taking trips in the car.

There is new stabilizer shaft on it and the Cardan shaft has to have been done at least one time, so not sure on its age.

On the plus side tires and brakes are good :-)

Planning to keep for long term.

Any thought on other things worth addressing now?

-Matt

gbstu

Matt,

Oddly I just had the same happen to my 2008 CTT, here's a picture of the corroded wire (brown and brown/red). I stripped, soldered and then applied heat shrink over the top, this fixed all the codes (in my case I was unable to get the vehicle in gear due to the parking lock would not disengage).



Thx, Stu

bigbuzuki

Fixing corroded wires due to moisture is good.

Finding and stopping the source of the moisture is better.

ScootCherHienie

Re. Age of Battery -- every battery I have seen in the last 30 years or so has a date-code sticker on the body of the battery, one of the 4 vertical sides usually. It typically says something like 5-13 for May 2013 manufacture date. You should still keep your receipt for warranty purposes, but you can always see the age of the battery ON the battery. The Cayenne battery is in a box under the drivers seat so seeing the label may not be possible without lifting the battery out of the box. I can see the date sticker on my current battery without removing the battery, but could not see the date sticker of the previous battery without removing it from the box under the seat. There are a couple of good videos on YouTube that show you how to access the battery of 957 series Cayennes. Very helpful to watch the video before the first try. I never would have guessed there are hinges in the back legs of the seat mounting bracket, for example. In Cayennes, the battery will likely last 8 years, more for very mild climate, and less for severe climate with very cold winters. And the electrical system does behave oddly when battery voltage is on the low side (like below 12.5 volts). If you have a V-8, every battery crossreference I saw would say H8 is the correct replacement size, but that is not accurate. An H8 doesn't fit the battery box properly because the length of the H8 is 13.5 inches and the battery box is designe for a battery that is 15-15.5 inches. To get the correct battery length (with the same battery post and vent locations and same width and height), you need an H9 battery. My car had an H8 when I got it and it would not clamp under the clamp that holds-down the left front corner. Taking the H8 out and replacing it wih an H9 filled the box correctly and the front corner of the battery now stays under that clamp on the front left corner as it should. This is also the sort of problem you see from odd problems like a bad ground connection somewhere... in your case, it would likely be a bad ground that has to do with operating the ECU responsible for generating the UBDII codes.

AusTexCTT

100% agreed i think I have taken care of the water issue by cleaning out the front two rubber drains. Left them off after learning as it's a poor design and prone to getting filled with debris, now it's an open 1 1/4 hole that's less likely to fill up

AusTexCTT

Quick update here until I can get my meter on the car and durametric codes, I am waiting on my Durametric delivery next Monday, in the meantime, I have run the car about 200 miles without using the seat warmers and other high draw accessories with zero error messages.

Planning next weekend as a time for a deeper investigation into this mystery.

AusTexCTT

Got my Durametric enthusiast cable yesterday, busy week this week so I'm planning to put the car in the garage next weekend and check the wires and alternator.

AusTexCTT

After a few weeks of driving the truck with 1-3 trips per week, wth zero issues, the original issues From my original posts recurred.

I metered the car voltage and had good voltage on the battery when car was off, had zero AC voltage when running. Charging showed at about 13.8.

I checked the battery and it was about 1.5 years old, still, I replaced the battery just to be sure, and I think the battery is fine.

I looked over all the wires in the driver's side floor and there appear to be no splices in the wires and no water evidence at all. That said I need to dig into the harness near the foot rest and beyond up into the dash.

So given that voltages are good both when off and when charging, with zero AC current, what would you check?
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