Yes I cleaned the TCM well, truth be told I found no oil in the unit itself, just on the floor and the harness, regardless, I cleaned the unit well, inside and out, with electrical contact cleaner and compressed air. I also took apart the connectors and cleaned each one as well as the harness.

After I had the exact same fault.

On cold start I can shift into both R and D and the trans engages, I can also walk it through 1234 using the shifter and all changes are indicated on the dash display.

After less than a minute it disengages although the dash indicator still shows the gear selection. At this point I can move the selector through the gears, all are reflected on the dash, however I can not toggle between 1234 and nothing will cause the trans to engage.

I clearly still have communication between the shifter and the TCM since selections are reflected on the dash, but engagement is completely lost and the worst part is that I am getting no codes.

I suspected that perhaps my Snap-on Solus could not read trans codes so I put a very nearly dead battery in the car and cranked it until flat. I then read trans codes and got a p2600 circuit 87 voltage low showing that the TCU had seen low voltage - so clearly the Solus can read at least some codes. I also ran the vehicle with the TCU completely unplugged, but this threw no codes???

I am very familiar with the valve body kits by Sonax and with the Contactor plate, but I would like to be sure before throwing more money at the issue. If I had a telltale code like speed sensor etc I wouldn't hesitate....

Has anyone heard of these symptoms???

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1971 Porsche 911 Targa RSR rep.
1968 BMW R60/2
1981 BMW R80GS-PD, dual plugs, 1000cc jugs, 10 gal "Gaston" tank.
1982 BMW R80GS-PD, duplicate of above.
1988 Neoplan/Mercedes 40' Bus
2002 SLK32 AMG
2013 Smart Electric