I am new to the group. I searched for info on this forum regarding my problem and got lots of good information, but not exactly what I need, so I apologize if this has been covered elsewhere that I did not see.

I have a '01 Excursion PSD with 140K miles. It is not a California truck.

My Service Engine light just came on and I took it to Advance Auto to have the codes read, it indicated PO672, PO674, PO676, and PO678 "Glow Plug/Heater." Reading online, I also see these codes indicating "Glow Plug Circuit Failure."

Seems to be only on one cylinder bank? Could this be the Glow Plug Relay? Suggestions?

Thanks in advance.

Jayson
Nashville, TN

 

Welcome to FTE. I hope this helps.

A lot of Excursions whether from Cali or not have a GPCM rather than a GPR;

This is the GPCM wiring diagram that shows the connectors to each bank.
If you had a GPR you would not get a code for a single bank or individual GP.
Check the connector at the GPCM and at the Valve Cover

 

What he said. Your Excursion has the Cali glow plug system (as does mine). Your codes indicate a problem with glow plugs for cylinders 2, 4, 6, and 8; one whole bank (driver's side), as you determined. This is done by monitoring the amperage pulled by each individual glow plug.

Short of having lost all four glow plugs on only one side (improbable) I'd suggest the problem is more likely in the wiring harness(es) between the GPCM and the bank; possibly a disconnected or bad wiring harness to the valve cover? Pull the plug to the VC and check for the connection, then "ohm out" all the wiring back to the GPCM. You can also check the GPs with an ohmmeter; on the VC plug the two outer pins on each end of that connector are the glow plugs. Check the ohms between each of those four pins and ground (the head) to see if any are dead.

Also, this guy's having a similar problem with his '99 Cali F.:
https://www.ford-trucks.com/forums/7...ode-p1396.html

BTW, GPCMs are $200 at NAPA, if it comes to that.

 

It was the GPCM. Replaced it and the Service Engine light went away. Thanks for the replies and data! Jayson

 

Many thanks to the group for assisting me a month ago in tracking down the faulty GPCM last month. But yesterday, my SES light came on again and I am now getting code PO683 "glow plug/heater module comm problem."

Has my new GPCM gone bad? Is it the harness? Was it originally the harness that blew the first one and now this one?

Thanks for any assistance.

Jayson
Nashville, TN

 

The first thing I would check is what kind of warranty your GPCM came with. Sometimes new parts just go bad.

You can also use an ohm meter to check the wires. Disconnect the harness from the GPCM and the valve cover and see if you get any indication of a short. Also inspect the plugs closely for loose or bent pins.