E55 won't shift gears

[Grahamcol]

This is on behalf of a friend who has recently purchased a 1998 E55 with 156k miles. Sometimes the box simply refuses to shift and despite a recent fluid and filter change it continues to play up. Initially I suspected the electro plate but switching off and restarting doesn't cure it. Also no code show up on a recent star test by our Indy.
One thing which does seen to make a difference is when one of the gears is selected manually, say 3rd, and then going into D afterwards seems to restore auto changes until the next time it plays up. Also I understand the car is more inclined to play up in S mode than in W mode.
I'm stumped on this one and so is my Indy.
Any suggestions as to the cause would be most welcome

 

[whitenemesis]

I'd still go with an electro-plate malfunction. Either that or selector module.

Either way fault codes must have been stored?

 

[Grahamcol]

Thanks. I understand no codes stored. That's what's baffling me. We've had the box ecu cleaned up because it was contaminated with ATF and the pilot bush replaced too to cure the leak. I've felt all along the problem is an electronic one but without codes it's hard to know what to do