[craigy_87]

Recently I've been getting some error codes pop up with a start assistance failure and transmission error.
The car wont tell me what gear it's in and seems to stick in the same gear and won't change.
Then it will randomly lose all codes an work fine again.
I've took a screenshot of the codes when they are there.

Seems like an issue with the transmission connecting to the DME as MHD monitoring shows the temp for the transmission as -40°.

Car is a 2009 335i with the DCT gearbox.

[CarAbuser]

Yeh no comms between DME and TCU. The two are connected by the PTCAN so you possibly have a wiring issue between the two.

Hard to troubleshoot, you could start by checking for any cable damage in the DME box area and check all connections are good and there's no moisture. After that you would have to look up a wiring diagram for the PTCAN and check everything manually which is tricky as I think the wiring for the DCT goes across the top of the box.

[craigy_87]

Well this all sounds fun, electrical issues ain't my thing

Thanks for the reply

[craigy_87]

DME end looks alright. I don't think I'll be able to check out the end at the transmission as like mentioned its on the top of the box.

[iqraceworks]

Check the main plug where it goes into the transmission...there is a chance the locking ring could be lose, and the plug might be working it's way out....

[Sac55]

Did you ever figure this out please?

[BRG_N54]

Originally Posted by Sac55

Did you ever figure this out please?

You do realize this was almost 3 years ago, right? The OP only had 4 posts, all in this thread and has likely never returned. You might have better luck creating a new post with the details of your issue, and we would be glad to try and help.