My car is in the shop with the following faults from the durametric:

(it's a Mk2 996 with the 722.6 mercedes transmission that is shared with the turbo)

DME: P0715 Porsche fault code 552 Tiptronic supply voltage speed sensors
Tiptronic: 13 RPM Sensor N3

transmission definitely hunts from 2 to 3 to 4

Transmission fluid level is ok, and it was changed 5,000 miles ago.

Dealer is saying it could be TCU or valve body.

I don't want to go through a $5,000 trial and error - what are your thoughts? in your experience which has been the most likely culprit of the two?

Thanks

 

Pull the valve body and replace the speed sensor if possible. There is a part number on the speed sensor itself. You may be able to get it from Mercedes. If not you may have to get a preferably new ($300) or used conductor plate. I don't think you can get conductor plate alone from Porsche. The valve body part number is identical from 1998 to 2009 for all tiptronic 911's regardless of model but I can't guarantee conductor plate is. See if you can get part numbers off conductor plate and speed sensor for comparison. I have both at home out of a C2 and will share those part numbers in a bit for reference. Send actual VB off to IPT for a rebuild and have the TCU cleared of faults and set to factory. IPT turn around is allegedly a couple days.

 

Also assuming they have already cleared the TCU once and the fault comes back?? I think that's a safe ER the sensor is the better place to start.

 

I cleared the codes 2X and came back within a day each....

Would that be safe to say the valve body is the culprit vs the TCU?

Thanks

 

Well, it would point me in that direction. But certainly doesn't have to be. It could be the harness, the 13 pin prong, or the input on TCU. You could always have resistance and continuity checks done on the yellow wire associated with N3 input. You may be better off at a Mercedes specific tranny shop if available as Porsche seems to have very limited ability to deal with these trannys..

A new TCU is probably the easiest to change but likely the most expensive in parts alone. It's also something you could do yourself. If you are handy at all with cars the VB is easy to remove and deal with and you could do conductor plate on ur own as well. Just make sure you are very comfortable with the fluid addition and check process!!

Regarding part numbers. The speed sensor itself for this C2 tip I have is 1402700069 and the conductor plate is 1402700561. Neither pulls a wealth of info on search. Actually a search for the plate yields almost nothing while a search for the sensor gets results for the plate. BUT....the conductor does cross reference to newer part numbers 1402700761 and 0161, 0361. Most parts will coincide with SL 55 AMG's and SL 500,600. Either way new from MB it's $270 and it appears to be even cheaper in these predecessor part numbers.

Seriously doubt its VB itself but likely plate or TCU. If it ends up being pulled certainly send it to IPT for performance build. Its about $700. Depends on ur level of expertise/guts/pocketbook as to the best approach. But if you do, while ur in there replace adapter sleeve with updated part number 68021352AA which is pretty cheap.

 

Pumptech - thank you very much for all your thoughtful replies...much appreciated.

The transmission definitely hunts around....

Another bit of clue:




I'm thinking the IPT modded valve body may be the route to go? or is the TCU likely culprit...

 

if you are in the market for performance upgrades or like doing upgrades while other parts are being worked on i think a new control plate along with IPT build is a good start. if you think you are going to have your tiptronic upgraded in the future you might save the VB for that time. it may still end up being the computer. its going to have to be trial and error to some extent anyway.

 

pumptech,

Thanks - they went through the diagnosis and they think it's valve body.
good news is that my service advisor went through a little more digging and found that Merc will actually sell the conductor plate and sensors separately from the valve body! (porsche only seems to sell the complete valve body).

Saved about $1K in parts from just buying the whole dang thing...

 

good deal! thats what i was suggesting. get the conductor plate from MB. should be about $300 but there are some available through other sources for less than $200. have them check the adapter sleeve to see if its newest part number 68021352AA ($10-15). send the actual VB off to IPT while they have it apart if you want some better shifting, but wait if you ever plan of tiptronic upgrade and have it all done at once. they can also put better solenoids in. let us know if the conductor plate solves the code!

 

here is same part number pat has on his turbo tip plate if you want it a little cheaper.

http://www.google.com/#q=1402701161&...=1177&bih=1255

 

Just ordered all new solenoids

http://www.makcotransmissionparts.co...6solenoid.html

 

Hi pumptech and pat - thanks for all your help.
It turned out to be the speed sensors on the conductor plate on the valve body.

They replaced only the conductor plate per your advice (THANK YOU) and she's all good again!

I would have ended up spending an extra $1,000 if not for your advice!

 

2 thumbs up!! I'm gonna do new conductor plate on this tranny I'm doing just because I don't know anything about this transmission. It's cheap insurance! I even saw some remanufactured ones for like $130!!

 

I have the same speed sensor fault and engaging limp mode on my 997 C2S. I have reset it twice. From your thread, it appears my cheapest option at this time would be to replace the speed sensor and the conductor plate. A few questions you guys might could help me with in planning this task.

Where is the conductor plate located? How hard is it to replace the conductor plate? Can it be done without removing the transmission? Is the speed sensor included when ordering the conductor plate?

Thanks for any additional help, this thread has already helped a lot.

 

speed sensor is part of the conductor plate and transmission does not need removal for this. this link will show you how simple the VB access is.
it is a very simple process to replace the plate itself. it requires removing the transmission pan, filter, and valve body which is all easy to do. even putting it back together is a pretty simple process but replacing the fluid and getting the fluid level back into correct tolerance is critical. too much, too little. or the wrong kind of transmission fluid is asking for trouble. any porsche dealer or mercedes dealer should be able to do this and for not much more than a transmission fluid/filter change. its about 30 minutes more work at most!

picture 1 shows tranny pan removed ( maybe 6 bolts) visible is the bottom of VB. pic 2 shows top of VB after removal (10-13 screws maybe) with black conductor plate which snaps in place once solenoids are removed. 3rd pic shows VB and conductor plate removed.