Cylinder 7 glow plug failure code

[EdSpaek]

My 2008 LMM lit the service engine light last evening and when I read the codes it indicates the glow plug for cylinder 7 has failed. I reset the code and it has not returned for several starts now. Does this make any sense. I have not read the resistance of the number 7 glow plug yet- plans to do so later today. Engine only has 78,000 miles on it. The Weather has been in the high 90's the past few days and I have been doing a lot of high speed driving and a fair amount of idling to stay cool, wonder if this has had any affect on the glow plugs or associated electronics

[DmaxMaverick]

Sounds normal. Glow plugs fail. Rarely is there a specific reason, short of excessive glow times. They just quit. It's a fact. Your highway driving and idle periods are not likely a factor, or we'd see a lot more failures. Your one plug may or may not be bad, so you should verify by testing. The PCM monitors the GP/heater system under specific conditions. On earlier models, if the sensed ambient temp and/or coolant temp is above 63°F, it isn't monitored. I don't know what the monitoring temp is on the later models. If your temps remain above this, you may not get a code, even with a failed plug.

Plugs fail for a variety of reasons. It is important to pull it if it's failed, to verify it isn't physically damaged, which could lead to pieces of it falling into the cylinder. If it appears intact, leaving it in will cause no damage, and only be an inconvenience when the SES indicator becomes annoying.

[EdSpaek]

Thanks for the info, had a second code show up after a cold start this afternoon so I disconnected the glowplug and had a resistance of 400 ohms so I replaced it and all is well. Do have a question, where is the sealing surface on the glowplug. I do not see a tapered surface only a flat surface where the heating element of the plug leaves the housing. Is that where it seals?

[DmaxMaverick]

It seals on the shoulder where the element exits the body. Unlike spark plugs, this keeps the threads out of the combustion chamber.

At 400 ohms, the plug should be good. They usually fail open. Put 12V on it and see if it glows. If it does, the problem may have been the connector.

[EdSpaek]

I will give that a try, the connections were fairly corroded so I removed all of them from bank one and cleaned and retorqued them

[Kennedy]

Suggestion: Dielectric grease

That and frequent "bathing" to remove road salt.