Three days after buying a 2004 Cayenne Turbo, there's no crank, no start, no obd communication, no gear shift PRNDL lights are all on...

Ray Barham · February 21, 2023

Do I have a doozy for you guys!!!

I bought an 04 Porsche Cayenne Turbo 2 weeks ago, and on day 3, I came out to a no crank / no start condition. The dash read "Press Brake to Start", so I replaced the brake switch and nothing changed. I left the key in the on position and disconnected the new brake switch. I then heard a beep and the car fired up without the brake switch. At which point, I shut the car off, reinstalled the brake switch and the car wouldn't start. So I removed the brake switch and drove the car home without brakes.

The next day, I drove it to the parts store around the corner to get another brake switch, thinking that the VW Toureg brake switch may have been incompatible. No such luck...as it was the same conditions as the other brake switch. I then drove to about 3 miles as which point, the car started "bucking" like a horse trying to get me off of its back. I stopped for about an hour as I went into my destination. When I came back out, it had a hard time starting and I had to rev the engine as the rpm's were dipping from about 2000 to 500 and the car would stall.

The gas a very low so I decided to limp to a gas station before heading home. After I got gas, the car would crank but not start. At each attempt, the crank would get slower and less powerful. So I called a tow truck but before the truck got there, the car fired up again but I had to keep my foot on the gas or else the car would stall.

Lastly, I drove it the 8 or so blocks to my house. Once in my driveway, I let it run while giving it gas as the rpms continued to dip. After a few minutes, the car stalled and I smell a strong wiff of gas...to the point where it gave me a headache. So I order a couple fuel pumps thinking that was the culprit but when I popped open the lid where the pumps are, it was dry as a bone. With the amount of fuel I was smelling, I would swear that the seat would've been pooled with gas.

Now, I have no crank, no start, no obd2 communication, no shift out of park, passenger headlight was flickering randomly, all of my Park, Reverse, Neutral, Drive in addition to the 1,2,3,4,5,6 manual shift mode are on. The codes I got before I got kicked out of the obd2 were the 0283, 0668, 0571 and 0700. Also, the old key fob was almost in shambles so I ordered a new key fob shell from ebay and put the old guts into the new key fob. After which, the key stopped locking/unlocking the door. When I got in to see if it would crank, the error came up reading, "Replace key battery" or something to that affect. So I swapped the battery for a 5023 and still no lock/unlock. Keep in mind, the car wasn't starting prior to the key fob swap...so this could be another issue compounded on the original cause or it could be something new and isolated from the no start issue.

Do anyone have any ideas?

Silver_TT · February 23, 2023

Never a great approach to use the "parts cannon" rather than true diagnostics.

You can't use a generic OBD scan tool with these cars, don't waste your time. Buy a Durametric which is able to read the proprietary codes and give you something of meaning when you are diagnosing issues.

I also suggest buying OE parts from Sunset Porsche using your VIN to ensure correct fitment rather than trying to guess that a VW Toureg part is the same.

Lastly, you may want to check your battery. I have seen a marginal battery cause all sorts of weird electrical gremlins. Just about the only thing I would do as far as throwing parts at it would be to replace the battery with a high quality AGM if the battery is aged.

Ray Barham · February 25, 2023

Thanks for responding. I went over to the Durametric site and checked out what their diagnostic tool can do. I own the icarsoft tool and am able to see the majority of the information that the Durametric tool offers. So I think I'm safe there. I'm attaching a link to a cloud folder with the pictures of the codes.

What I was able to do since my OP was verify that the starter is good and I got the scan tool to connect to every system except the DME which gives me a "no link...turn on your car idiot" message. I got a plethora of fun codes that points me in every direction and no direction at the same time. I'm starting to suspect that there's something going on with the ECU or a close relative. Here's my reasoning:

Intermittent Brake Switch Issues

Passenger High Beam Strobe Effect

No Communication with DME but can see every other system

Dash Digital Display Completely Died Yesterday

No Transmission Shift

Intermittent Dash Codes Flashing then Clearing itself