Can anyone explain the faults being indicated with the illumination of the check engine light on a 300tdi.
The engine starts fine, runs fine, no smoke, no worrying noises. But, at very low speed, in slow moving traffic for example, 1st gear (auto) about 1400 rpm the check light illuminates, it is very precise, the exact speed/rpm/gear every time, any change in throttle position clears the light. The warning does not come on in neutral at any time through the full rpm range.

Is it an oil warning light? If so change the oil pressure switch - not expensive and easy to replace. If that doesn't cure it take it to a specialist.