Chrysler Grand Voyager recurring limp mode

Hi, I am a disabled driver in the UK and own a Chrysler LX Grand Voyager (Graz built GS). It is equipped with the 3.3 L Petrol engine and the 41TE Autotransaxle with a total mileage of 140,000 on the Odometer. The vehicle is serviced regularly and ordinarily runs faultlessly.

Eight weeks ago the vehicle suddenly failed to engage 3rd gear whilst gently accelerating before dropping into limp mode. Immediately before this occurred the engine very briefly cut out twice (almost a misfire as re-engaged instantaneously), this had occurred randomly on several previous occasions during the preceding 3 months but had NO adverse effect on the transmission shift so not sure if this is even relevant.

Unfortunately as my income is extremely limited taking the vehicle into a dealer is outside of my budget. Maintenance & repair is therefore conducted with the assistance of friends or through smaller shops who's expertise is limited.

With this in mind the diagnosis of this issue has been limited to reference to the Internet with assistance from OBD fault code checking at a small (non transmission specialist shops). No codes were obtained and communication with the TCM was not possible.

Whilst there were many of these vehicles sold in the UK it appears few garages possess the diagnostic software which can interact (other than occasionally on a very basic level) with Chrysler's onboard OBD II diagnostic/programming system. Thus it is possible that the lack of transmission fault codes may be indicative of equipment incompatibility and thus a failure to recover any codes RATHER than a total absence of any codes in the first place. Thus it is perhaps a false negative?

In the process of troubleshooting this transaxle issue, the fluid (Mopar ATF +4) was checked for level and condition. In fact the mechanic considered the fluid to be in such excellent condition (neither burned, contaminated nor discoloured) that he chose to reuse as much as he could before topping the level with fresh Mopar ATF +4. The filter & gasket were also replaced, noting that the pan magnet was found to be totally clean on inspection without even the faintest trace of metallic deposits.

Subsequently both input & output speed sensors have been replaced along with the shift solenoid using the latest available Mopar OEM replacement (new) parts.

Despite all of the above remedial actions the vehicle continues to fail to engage 3rd gear and above and simply drops back into limp mode.

I would very much value any suggestions, thoughts, assistance you might be able to offer as what/where to look next. Also any guidance on replacing the TCM (I have one sitting on a 98 LE with a damaged engine I keep for spares) and what is involved (what, if any, re-programming is required) other than disconnecting and refitting?

A .pdf of a 2000 NS Diagnostic Procedures Manual for the Transmission would also be very helpful if any forum members can assist or point me in the right direction. NB. I have the Powertrain Diagnostic Procedures Manual but this does not really cover the A604/41TE Transmission and how to troubleshoot any issues (especially electrical) in situ.
All/any help you can offer will be very much appreciated.

Many thanks,

Voyager Pilot