guruab

Ok hoping to get some answers here on this issue I am having with 2004 Porsche Cayenne S with 132k Miles. Just bought the car from auction. Check engine light is on along with Warning Brake Proportioning message along with Flashing brake light and a Yellow Exclamation Mark. Speedometer doesn't work. Check engine light had several communication error codes along with a Vehicle speed sensor code. Here is what I have done so far with no success.

Changed all Wheel speed sensors
Changed Vehicle speed sensor aka Crankshaft sensor (On Bellhousing)
Changed Rear rotors and Pads as they were shot.
Changed Brake light switch (Code for that as well)
Changed all 4 tires as previous owner had mismatched sized tires. I put 275/40/20 all around

Car is still stuck in 2nd or 3rd gear and Lights are still flashing. Only code gone are Vehicle speed sensor code. The speedometer still does not work.
I have felt carpet it doesnt feel wet nor is there any foul odors inside assuming water damage.

Also battery was DEAD when delivered from auction. We put a charge on current battery and its back to full health. Have not changed battery though.

Should I start ripping apart carpets to check wiring now?? Has anyone had this problem? I've read on similar problems with water leaks , but my car always starts fine and is never stuck in park. Could it still be related to corroded wiring? I took it to a german independant specialist and they recommended I take it to porsche. They hooked up their scanner and got 25 codes for No communication to abs modules, tiptronic modules etc..

HELP, need some guidance

J'sWorld

In this instance it would be wise to first rule out your battery as a problem. You can run the gamut of test and try to get all scientific about it or you can just put a new one in and move on with your life. The brake error number one likely cause is a vacuum leak in the hard line that runs from the vacuum pump to the brake booster. It usually cracks near the coolant expansion tank Communication errors could be caused by the battery. Some fault codes needs a dealer to erase and may be an issue until they have been.

guruab

Thanks, I will bite the bullet and try battery First.

ventoGT

If an indy tells you to go to Porsche, get another indy.

JAGMAN1

It sounds like either the wiring corrosion issue or a failing terminal 15 relay. The terminal 15 relay is what powers all those wire bundles that run under the carpet. A relay failure will manifest with similar symptoms to the corrosion issue.

The relay is mounted atop the battery under the seat.