2009 Cayenne V8 Electrical problems from broken wires

[touareg]

Long story short, one day noticed water in the drivers footwell, found a leak on the door to body wire harness. Dried car out. Car was 100% before this, seemed to be OK even when wet.

 

2 Weeks later, car started getting random faults on the MFI (Brake, ABS, PSM, etc). Would clear, then come, then clear. Battery is about 7 months old (replaced when I first got these errors) Ton of errors in durametric, then one day would not start or move out of if it did start.

 

Peeled carpet back. Found 3 wires. 1 Crimped, 2 soldered. 1 of the soldered was gone, so cut that out, butt soldered and then repeated for the other 2 as I heard they usually go bad.

 

Cleared all the DTCs with durametric, car started fine, all looked good in happyville.

 

2 weeks later got a check engine light, read codes, p0119, p0117 and p1552 (from memory, may be wrong). Seemed to be the engine temp sensor. Thought maybe a fluke, reset and ignored. This has been on and off last few months.

 

I also noticed when hooking the durametric, or other code readers, it seemed to create a draw on the system, and the engine would idle rough, or the e throttle would not respond if I tried to drive with it plugged in. Pulled the durametric and all was fine, same with a bluetooth ODBII module I have.  I replaced relay 433 under the driver's seat, and this seemed to cure that problem, since it provides relayed power to the CANBUS.

 

About 3 months later got a PSM failure, at 45MPH and car went into limp mode. Restarted car, error was gone. Seemed fine for another month, got the same PSM failure yesterday, car seemed to be lurching a bit in slow moving traffic when it came up.

 

Could the bad temp sensor be triggering this? It has slowly gotten worse I assume as once in awhile I see my gauge stops working. Or did I miss something else with my wire repairs.

 

I am at the point ready to rip out passenger wiring under the carpet and inspect, but I suppose I should just replaced the impossible to reach temp sensor first, as it really does seem bad at this point.  I also notice all the fuse block fuses for the PSM are on the right hand side, makes me wonder if the wiring issue is there.

 

Just seems weird I have all these problems at once.

 

Edited April 19, 2017 by touareg

[solo25]

I'm troubleshooting mine as we write. Occasionally, I'll depress the brake pedal and try to start the car and it won't. I've learned that when that happens, if I pump the brake 3 times (2 won't work), the car will start. Then the Brake Proportioner /ABS warning comes on and the car is stuck in park. Then, after a few minutes or less, I hear a click and I can shift and drive normally, but with the engine light still on. I've pulled up the driver's side carpet and it's not wet and none of the many wires seem to be corroded. Lately, I've noticed that if the car starts and won't shift, a good stomp or two on the floor with my left foot will cause the problem to stop. That leads me to believe it IS a wiring problem, but what should I look for?

[touareg]

If you have an early cayenne, the brake switch was known to go bad, hence why pumping the brakes works in your case.

 

http://www.pelicanparts.com/techarticles/Porsche-Cayenne/37-ELEC-Brake_Light_Switch_Replacement/37-ELEC-Brake_Light_Switch_Replacement.htm

Edited April 19, 2017 by touareg

[lewisweller]

6 hours ago, solo25 said:

I'm troubleshooting mine as we write. Occasionally, I'll depress the brake pedal and try to start the car and it won't. I've learned that when that happens, if I pump the brake 3 times (2 won't work), the car will start. Then the Brake Proportioner /ABS warning comes on and the car is stuck in park. Then, after a few minutes or less, I hear a click and I can shift and drive normally, but with the engine light still on. I've pulled up the driver's side carpet and it's not wet and none of the many wires seem to be corroded. Lately, I've noticed that if the car starts and won't shift, a good stomp or two on the floor with my left foot will cause the problem to stop. That leads me to believe it IS a wiring problem, but what should I look for?

In the bundle the black cables that are factory crimped together are they looking good?  Why not run some solder over them and then shrink wrap them.

If not redo all the soldered and crimped/connected cables, tedious work but you'll have to eliminate this first and its cheap. 

 

Brake Switch is on the pedal for 2004-2005 but in 2006 onwards its built into the master cylinder. I have a new oem brake Switch if you want one? I found out the hard way lol mines not on the brake pedal. 

 

Edited April 20, 2017 by lewisweller

[solo25]

Thanks, you sound like you've been having some of the same problems as me. Here's one for you. Sometimes, the car starts right up. Then other times, I'll depress the brake pedal, turn the key....and nothing. Then, if I pump the brake pedal three times (not two, it has to be three), it will start, but stay stuck in park for a few minutes with all the dash lights and warnings flashing.. Then, it will release and I can drive it. I've found lately that if I reach down and wiggle the bundle of wires, it will unstick out of park, so that leads me to believe that the wires are the problem, but I don't see and corrosion or crimped wires. You wouldn't have a photo, would you? If not, where exactly should I look" Near the seat or toward the footwell? It's encouraging to talk to somebody who seems to know what I'm going through. As for the brake switch, I thought of that and might be interested if I can find out that's the problem. Is it a DIY project?

[solo25]

Toureg, thanks. I seem to have repeated myself here. It's a 2009 Cayenne GTS, so if what i read is true, the brake switch is part of the master cylinder. I still wonder why fooling with the wires under the carpet seems to solve the problem. tomorrow I'll take lewisweller's advice and look for the black wires, but I have looked at the bunch in general before, and don't see any solder or crimping. I must be looking in the wrong place. Can anyone provide a photo or diagram, or a more exact description as to where the wire are that I need to look a? I can see those that run from under the driver's seat toward the firewall.

[touareg]

Your looking in the wrong place, for me it was easy to find, as the black wrapping had green stains from copper oxidizing, plus pushing it while the car was running caused errors on the dash.  You litterally have to unwrap the wiring harness, just above the flat plastic black channel as the wires head towards the dead pedal.

[touareg]

I have purchased a new code scanner, durametric is a piece of crap for cayennes that I have had. I was able to pull a code today, for the PSM, 1314 not being able to talk to the DME, it was logged when I lost power today at highway speeds. Restart or the engine (did not even have to shut the car off all the way) fixed the issue per usual.

 

No codes anywhere else. So my PSM is either flaking, or the canbus wire is bad for it.

 

Where is the PSM module located?

[touareg]

It is under the DME, and talks to the DME on a can drive bus.

 

I wonder if I have moisture or other gunk in there and that is what is causing this issue... Going to pull and clean all connections this weekend on the DME and PSM.

[Boune]

Hello Touareg
I'm coming to you because I have the same problem on my Cayenne GTS 2008 porsche.
I have engine crashes in degraded mode with the PSM LED on. 
When I query the DME ecu I have the error codes P1552, P0117, P0119 and in the PSM I have the error 1314 (DME fault communication).
I checked the DME relay and the ground of ecu but nothing. 
After a long search I changed the DME ecu but the problem comes back. 
I checked the beams but I did not see anything. Have you solved your problem? 
Thank you in advance and sorry for my bad English.