Hi all.

my partner broke down in her s max yesterday with the error message ‘transmission limited function’ on the dash.

I plugged into it when I got home and got the following codes: P0766:00-24, P0949:00-27.

 

After a bit of research, I was thinking that it would be an issue with a solenoid in the mechatronic unit, so took the airbox off so I could assess how big the job was likely to be.  (For reference… I’m not a qualified mechanic, but worked in a bodyshop years ago and have always worked on my cars changing clutches, brakes, head gaskets, general servicing etc)

I read on here that the issue could be linked to the battery and to charge the battery overnight to see if that solved the problem. 
 

This morning, I took the battery off charge and attempted to test drive the car to see if a charge helped, but the car broke down almost immediately.

 

i now have the following codes:

U0101:00-08

U0401:68-08

U0101:00-28

U0402:12-6c

U0402:68-2a
 

These seem to be linked to a communication problem.  I’m wondering if me having a look last night and disturbing the wiring loom could have caused this, and perhaps the actual problem is wiring related.  
 

I did not unplug anything last night, I simply checked how much slack was on the loom to assess space for removal of the mechatronic unit.

 

Has anyone had a similar issue or can shed some light on this?

 

much appreciated.

Ok… so I’ve spent some time looking at the car tonight and I noticed that the wires/loom going to the mechatronic unit were under a lot of tension, as the main loom that the wires go into were not supported anywhere and the weight of the loom was hanging off of the mechatronic multi pin plug.

I took the plug off, unwrapped the insulation and using a pin to poke into each wire, I was able to check the continuity of several of the wires. On at least two of the wires, the continuity breaks when the plug is moved. I’m confident that this is the cause of my issue.

My only worry is that the break will be so close to the plug, I will not be able to repair I won’t get a soldering iron in to where the break will be.

Does anyone know if Ford sell this plug, prewired, ready to be soldered onto the existing loom. Or… does anyone know how to remove the pins from the plug so I can replace the wires?

Sorry for not responding straight away, we get loads of one post wonders on here who ask technical questions then clear off and never come back to read the replies.

So, you're definitely barking up the right tree suspecting electrical issues first, before throwing loads of parts at it

Get all of the wires from the transmission to the TCM and the TCM to the PCM checked for continuity and repaired or replaced as necessary.

The main culprit on yours is a large multi plug in the LH front wheel arch, the wires break going in and out of the connector plug.

Also ensure all the earth points are clean and working properly and the battery voltage is good.

10 hours ago, Craig Barnes said:

Does anyone know if Ford sell this plug, prewired, ready to be soldered onto the existing loom. Or… does anyone know how to remove the pins from the plug so I can replace the wires?

They don't, no.

An auto electrician will know how to de-pin and rewire if needed

Hi Dave. Thank you very much for your response. I am going to check the connections myself and see if I can spin the plug to repair the wires. If I’m unsuccessful, I will call an electrician to take a look at it.

SY Diagnostics used to have a solution for the under wing connectors on his excellent You Tube channel (before it was hacked - he's trying to build his channel back):
https://www.youtube.com/@sydiagnostics2025
His option, when he found a wire in the multi plug that could not be de-pinned was to simply bridge that specific wire from one side of the plug to the other. Useful if you can't get a plug or there's corrosion etc?
I've also seen a direct wire from the PCM circuit board through the case to the wire harness which saved the need for a new ECU.

Well Done for tackling all the external first and I'll simply ask, when was the oil and filter last changed and give my usual suggestion:
https://www.ebay.co.uk/itm/112436788478