2001 E38 740i Sport Trans Fail Safe error

[Robs740iSport]

For the last week or so I have been getting Transmission Fail Safe and my speedo and tach stop working, The car runs perfect until it warms up then the trans fail safe error appears its also accompanied by these trouble codes.
p0600 -serial comm Link Malfunction-
and P1747 -transmission-

The Transmission shifts perfectly until the the fail safe program so I don't think its the transmission. Any ideas?

THANK YOU!

[Drkenigma1]

I had a similar problem. I drove over a speed bump too quickly and a few minutes later "just the trans fail safe error popped up. But in you case did three lights also come on? I have an X5 and that problem turned out to be the water cooled alternator which dealer lists at $900

[brettski]

Welcome to the Werkz (both of you)

There is a little control box on the oil line between the oil cooler and the torque converter on the front lower left hand side of the engine bay, I thnk that it a solonoide but I don't know for sure, I think that unit controls the oil flow to the cooler and possibly may be failing to activate. Start the car once its stone cold and let it idle and see if it eventually activates once its all warmed up. Just a guess, not really sure though.

The other option is take the car to a specialist Auto trans service shop and get the fluids and filter changed, that can solve a variety of issues, some of which are seemingingly unrelated to the gearbox.

[Gramonion]

I have an E38 and had a similar problem also.

It happened when I bottomed out on a dodgy piece of road.
Except I could only get 3rd and reverse gears.

Turned out that the cable for the electronics to the gearbox had gotten squashed and and shorted out. Well that's what the garage told me anyway.