Make sure it lights up when you turn the key...maybe the bulb just burned out.

Seriously, they CEL will reset itself, but if it was the GP circuit at fault it will come back.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Just put the tester on them and I got the following results:
GP5=136 ohms and the rest GP1 GP2 GP3 GP4 GP6=0.6 ohms
Now how to identify the GP on the engine?
I also looked with a flashlight under the manifold and all 6 of them looked new to me.

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New Addition to the family
2013 Passat TDI 5Miles
2004 E500 4MATIC Wagon 95k
1996 E300 Diesel 173k Sold
1993 300E 2.8 230k Sold
1994 E320 White Wagon 373K Sold
Still dreaming about ....500E


Radu Negru

I believe they are numbered to match the cylinder numbers so #5 is second from the back. That's your faulty plug and that is the reason for the CEL. Again, if you paid the dealership to change them less than a year ago I would complain to them and let them re-replace #5 as it is under warranty. If they balk speak to the service manager.

It's a time consuming job to get to it as they will have to pull the intake manifold and would probably charge 2 hours labor, or $200+ just to replace the one bad plug now. If they have a clever tech with enough experience he might just be able to do it without pulling the IM, but would still charge you for the time it would take to do it anyway.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz