Mechatronic unit problem - perhaps !

[Altomar718]

Hi All - Help please?
I have a Merc C320 CDI with 120,000 on the clock (08 plate). The problem is, when I take in on the motorway running at constant 70mph (it is fine around town etc.) for no reason, it goes into a sort of 'limp mode' - The automatic gears dont work, it is gutless, and the only way to change gear, although acceleration wise it doesn't make much difference, is to put it into the C or S setting and then use the paddles to change gear. I have taken it to a Mercedes equipped garage who said there are no codes stored ! They went through and did another clearance and I took it for a run and did 85 miles .... suddenly into limp mode ! If it is parked up for a while, starts and runs perfectly !

The garage checked wiring to the Mechatronic unit etc. but said they think it is probably that - BUT - at a cost of over £2000 to change it, I am a bit concerned it could be something else and I've spent £2000 for nothing

Has anybody got any experience or help on this please?

Thanks

Chris

 

[AMGeed]

When was the ATF last changed?
That is where I would start and I'd get a Mercedes specialist to carry it out.
I wouldn't use just any workshop, but one where the owner knows the car.

 

[KennyN]

I think you need to establish exactly what your mechanic is talking about regarding this Mechatronic unit.

Does the car have a DPF ?

K

 

[Altomar718]

Thanks for the replies KennyN and AMGeed - The garage I used is equipped with all Merc diagnostics and equipment, but not a Mercedes dealership. DPF, I presume so as it is diesel and as for the ATF, it has been checked. The fault seems to happen when the cars been at constant speed (70,ph) and then slow down to say leave one Motorway to join another - not long after that, limp mode !