Code 5 is attributed to a plugged EGR tube.

Tube runs from right hand side (exhaust manifold) behind the head to under the intake.

The carbon cokes up at the intake end of the tube.

Some people have had luck running a speedo cable chucked into a drill to clear the obstruction. I didn't. I think that stuff is harder than diamonds.

I pulled the tube at both ends and cleaned it out. No light since.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles