Hi all,

Currently working on getting a salvage title Cayenne S 958 back on the road (Purchased form salvage auction to rebuild and drive as my DD)
So far i have replaced the battery & pyro fuse to get the car starting. Car now starts and i can even drive it, but only using the shift interlock bypass due to an error message on the dash "Gearbox Emergency Operation" In red.

The error codes i currently get are:

• P070900 - Transmission range sensor, open circuit
• P0700 Transmission Control System (MIL Request)
• C12082 - Check Transmiss. control unit fault memory content
• 000125 - PSM Activation by PTM
• U0414 - Check Transmiss. control unit fault memory content
• U0402- Check Transmiss. control unit fault memory content

Based on above i suspect the transmission range sensor (Neutral safety switch??) fault?

Any help on troubleshooting is appreciated.
-Scrotius

 

How did the vehicle end up with a salvage title?

What is the freeze frame code and data? That's the code that triggered the CEL.

No access to the Porsche OBD2 reference for the vehicle but when I see codes starting with 'U' those take precedence over codes that start with a 'P'.

Another reference:

U0402: Invalid Data Received From Transmission Control Module

U0414: Invalid Data Received From Four-Wheel Drive Clutch Control Module

The 'U' codes point to a problem with the transmission control module and the four-wheel drive clutch control module. In this case a sensor error can be collateral damage so to speak arising from the primary problem.

 

Hi Macater,

Thank you for your reply.

The car was rear-ended which resulted in the bumper, crash member and lift gate being damaged and the Pyro fuse blowing - No airbags deployed and so i would think the impact was not so severe to have damaged the driveline.
Also may be worth noting that the battery was completely dead when i took receipt of the car so i have had to replace this too.
(I uploaded some pics in this thread: https://www.6speedonline.com/forums/...cayenne-s.html)

I am not familiar with Freeze Frame codes so will read up on this tonight and get back to you.

I believe the TCU is located under the passenger seat. I will pull this and take a look to make sure there are no loose connections etc.

I really appreciate the help.

 

Freeze Frame data attached as requested - it appears the P0709 is causing the CEL.

 

In some cases when a vehicle is declared a total loss it receives no consideration. In one case I know of word came through a car on the body shop's lot was declared a total loss. An employee got up and went out to the car and started the engine and even though the front suspension was heavily damaged and the steering of one wheel was broken managed to maneuver the car around to get it more out of the way. When I said something to the body shop employee about what he just did he just shrugged and said "Its totaled."

In the case of your Cayenne it could have left out side with the one or more windows down and water could have gotten into the cabin. Or from the impact a normally watertight cabin was no longer water tight.

 

Hi Macster,
So you are suggesting it could be water damage in perhaps some of the modules / wiring?

I guess it is certainly possible - I will look for any evidence of water ingress - although everything seemed dry from an initial inspection.
Also - because the power was completely dead on arrival i didn't consider the possibility that the windows were down at any point, but i will certainly have a look.
Is there any specific location you recommend looking at first?

Thank you again.

 

Water damage is a possibility. If you are sure there is no damage to the wiring harness from the damage the vehicle experienced when rear ended not sure what else there is.

Not sure what if anything is on the cabin floor in a Cayenne. But check the cabin floor for any signs of moisture. This will at least let you know a portion of the car was exposed to the elements.

The moisture though could have come and gone. I'm reluctant to send you down this path but you put yourself on this path by choosing to resurrect a salvage vehicle.

So carefully expose and carefully examine the security module and the engine control module for any signs of water damage. And the transmission module too though where that is I have no idea. Maybe in the transmission in which case it should be immune from water exposure.

I note you provided the freeze frame data and it is from DTC P0709 which points to the sensor.

I could be wrong in that one's focus should be on the 'U' codes. If the wiring is ok and you see no signs of water then consider replacing the sensor.

Without the proper factory manuals and training and experience of a Porsche tech you are working at a disadvantage in that you do not have the resources to first make a high confidence diagnosis. Thus throwing parts at the behavior is I guess acceptable. 'course, it is your call. I'm loathe to advise one to go down this path but you can do what you feel is the best thing to do in your situation.

 

At 12V the battery is at 25%. So that 11.83V is suspect. These vehicles do not do well with low voltage levels.

 

Thanks again for the advise and support Macster.

I have put the battery on charge - I did this a couple of weeks ago when i first replaced the battery but didn't realize it had dropped so much...

I've spent some time researching the Transmission range sensor and as i understand, this tells the ECU / TCU what gear the car is in.
One thing i noticed is that when the car has the key turned to position 1 (No ignition) the gear selector indicator shows up and i can make it shift trough all gears. As soon as ignition is put in position 2; the little red indicator disappears as though the car doesn't know what gear it is in?

I agree with you and think it is likely either a wiring issue or a transmission range sensor fault so i have ordered the sensor itself (for $40 i figure its worth a try) and while i wait for it to be delivered, will spend the weekend looking through the associated wiring harnesses to see if i can find anything unusual.

I have purchased the workshop manual and have started working my way through it - Also, I had no illusions when buying the car that this would be easy and i know i set myself down this path (mostly as a learning experience) but all the same i do appreciate your concern

Thank you again for the help.

 

Spent some time working on the car today and pleased to say I got this portion of it fixed!

it turns out that while the car was sitting in the salvage lot that a small critter may have made it his home and nibbled some wiring. Took the entire floor off the passenger side and repaired two chewed up sections of wiring harness and error codes are finally gone!

now on to getting the seatbelt replaced...

Thanks again for your help Macster.



Section of chewed wiring

More chewed wiring

Errors cleared off dash and gear selector finally working!