Hi guys got a volvo s40 1.6d on a 56 reg customer complains of a loss of power and engine light on every 3-4 days problem goes when engine switched off or codes cleared and left a short while.another garage has had a look at this and suggested a faulty egr valve but i suspect this is mostly guess work from looking at the codes.

codes on my modis are as follows:

9110 control valve inlet. signal low (egr throttle)
6110 electric cooling fan signal low
6820 turbo control valve signal low (vane actuator)
1320 mass air flow meter faulty signal
6630 glow plug faulty signal

to check the egr theory first of all i have taken this on a 20 mile test drive to view live data and removed the egr to check operation i carnt see any problems with the egr in live data or by operating it off the car, have cleaned it any how and refitted i have also oprated the turbo vanes with a mity vac they seem free and easily worked .
using a ford focus (same engine) wiring diagram i have noticed all the components the codes relate to are supplied by the same fuse, when fuse removed exactly the same codes are stored. i am now thinking that the problem is down to a supply voltage issue although at the moment (car running fine/problem not present)i have good battery voltage at these components i have had a good pull round on the wiring loom whilst checking supply voltage and carnt find any breaks.
can anyone offer any advice from here do you agree with my diagnosis so far and has any one had this before or have experiance with these 1.6d s40's any suggestions would be a help sorry for the long post
thanks lee