Code PO677 (glow plug)

[LEE BROWN]

Engine light came on my 06 GMC truck. My buddy checked it with his Snap on Modis. It said code PO677 #7 glow plug circuit. He reset it and it went off but came back on the next morning. Is this more than likely a bad glow plug? If so is it as easy as a spark plug to change and also which cylinder is #7? Thanks.

[DmaxMaverick]

A glow plug code that specifies a cylinder is almost certainly a bad glow plug (after confirming the harness is not at fault).

They are almost as easy as replacing spark plugs. The connector needs to be threaded off (nut), GP removed (just like a spark plug), and replaced in reverse order. Do yourself a favor and use some anti-seize (nickel/silver, not copper) on the threads.

Cylinder #7 is the rear/right (closest to the passenger seat). #1 is the forward/right (furthest from the driver seat). Cylinder banks are odd/even. All odd cylinders are on the passenger side, counted from the front (1, 3, 5, 7), and the even cylinders are on the driver side counted from the front (2, 4, 6, 8).