Coil light flashing and drives in limp mode

[Norman]

I bought a audi a6  2010 about 3 months ago but 1 the fan keeps goin when you switch it off been back to garage he still carnt find the fault plus its just been back in for the coil light on and limp mode picked it up after he said he fixed it but today it came on again don't know what mechanics he uses but I question there ability  it's needs to go back in need some points to least to tell them 

[Steve Q]

It needs a diagnostic check for a kick off to see what fault codes flag up

[Norman]

I keep telling them that but don't know what there doing looks like I need to do it myself didn't want to as the car is still under guarantee 

Thanks