Link: Macclesfield MOT & Service Centre
Year of Manufacture *: 2007
Engine Size and Code *: 2.0D 640.941
( Optional ) Scanner Used: Autodiagnos MTPro
( Optional) Fault Codes: P2197 & P2199
Car came to us as a non-starter and the two DTCs set telling us to check the Y94 Quantity Control Valve for Open Circuit or Short Circuit to ground.
Searched the web and found some information on this CDI3 system. Now understood what this valve did and realised that mainly it is used to control the quantity of fuel injected at high engine speed. But that it should be wide open during the starting phase to allow pressure sensor to control the fuel rail pressure and hence starting. So that explained the non-start situation.
Checking the valve and wiring, we found a short to ground on one of the wires from the ECU to the valve. Quick check of the wiring revealed the harness pass over a metal forked clip on the blukhead held in place by a ty-wrap. This arrangement allowed the harness to rub through shorting out several wires including one to the Y94 valve. Insulating the wires and re-routing the harness in the clip and the car starts and run fine.
Not sure if this clip has been moved and refitted badly or just poor quality on Mercedes part.
The photo below shows the offending the clip.
Hope this helps someone in the future.
Sean
Message Thread
« Back to index | View thread »
Copyright © uk autotalk