2005 e320 cdi:

Glow plug preheat light didn't go off as usual today and I inadvertently started up anyway but turned the engine off right away. Turned the key on preheating coil again didn't go off. Turned the key off then tried again and everything was normal; car runs fine except the check engine light is on.
Scanned with my MBi980. No codes but scanner said to check the wires between # 6 glow plug and preheater. I have searched Google can't locate cylinder numbering????? Is # 6 at the front or the back?

Anyone with an opinion on what happened and the fix?

The other question is how to shut off the "check engine light"?

I can't answer your questions about the computerized gizmos, but a straight 6 will have the #1 cylinder at the front and #6 at the rear.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Any low cost OBD2 device should be able to handle this. Personally I like the Autel MD802, it also has all the Mercedes-specific stuff to talk to all the various computers in the car.

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1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

Got it sorted out. Bad glow plug. Came out no problem at less than the specified max torque of 18ftlbs (25Nm).