I purchased a Mercedes-Benz E320 CDI automaticin January and on a recent visit to a garage it exhibited the following faults:

P220A The speed comparison of Y3/6n2 or Y3/6n3 is implausible
P2502 The gear is implausible or the transmission is slipping

I was told it would be a £1500 to £1600 gearbox re-build. I have since done some research and come up with a lot of possibilities and would very much appreciate your input.

The suggestions I have heard have included:

Battery problem and a replacement battery will fix it
Speed sensor needs replacing
Fluid level needs checking and adjusting
Oil leak onto gearbox affecting the electrical connection
A valeo radiator leaking into the gearbox and a glycol test needs to be done

It would appear only the final problem would warrant a complete strip down and re-build of the gearbox.

I am loathe to dump the car as I cannot really afford to do so, however I do not want to pour so much money into it only to discover more problems.