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P0671 Cylinder 1 glow plug circuit
Have this error code, found this on another site, does this sound legit?
Is it a HARD P0671 fault (as in the code remains even after you attempt to erase it)? If it is, the way to diagnose it requires use of a DVOM. Set it to measure Ω. Start by disconnecting the the connector to your glow plug buss bar to bank #1 glow plugs (this will be the connector with the red lock tab that needs to be released before you squeeze and pull to disconnect). Measure the Ω reading between the wire that goes to the glow plug closest to the front of the engine on the passenger side, between the connector and battery ground (negative battery post on the passenger side battery). What reading to you get? It should be between 0.5 to 2.0Ω. Any greater than that, means the problem is either the wiring that goes to the four glow plugs on the passenger side bank of cylinders or the glow plug itself on cylinder #1. If the reading is within specs, measure the Ω reading on the white with light green stripe coloured wire between the connector you disconnected and the green connector to the GPCM on the passenger side valve cover. The reading you get should be less than 5Ω. If it's any greater than that, the problem is in the engine wiring harness. If it's less than 5Ω, and the wiring to cylinder #1 glow plug checks out good, replace the GPCM (Ford Part Number DY-876).