Tayfun

I own a 2002 e220 CDI but while driving not in city but longer roads where i can drive 120 fixed or more, my turbo suddenly deactivates so i have to turn my engine off and on to activate it again. It deactivates after a while if i go 100-120kmph fixed but if i try to go around 140kmph it just goes off in a shorter time.
Checked turbo pipes by applying air pressure, no leaks. Any idea where the problem might be ?

PSDCampervan

It's most likely a V.G.Turbo (variable geometry) so a servo commanded by ECU makes subtle adjustments to a slide ring that adjusts fins on exhaust side of turbo impeller to increase or decrease boost based off engine's load demands. These adjustable fins on impeller wheel can overtime become 'coked' up by carbon residue from exhaust gasses which then causes increased impedance to their full range of motion during servo adjustments which can consequently cause servo to 'bind up' The VG turbo servo will send a fault message to ECU which will set a code & switch it into to 'limp mode' RPM control. During next drive cycle, ECU will 'forget' about limp mode actively (it still 'stores' previous DTC in memory but won't become 'current' again) until parameters required to set it (usually hard acceleration) are reached. That was my experience anyway. R&R of turbo cassette & servo driver fixed the problem for me.