Glow Plug recommendations and issues...

[toobsluver]

Found this, this might help....

https://4656923915310766587-a-1802744773732722657-s-sites.googlegroups.com/site/woodnthings8/2002-f-350-superduty/maintenance-articles/GPCMTestingProcedures.pdf?attachauth=ANoY7cqMhjKvZkJZhVjV7cFENoWU8M-RHNOh9lA9swUPtTGYnC-RL9Xgzx75Y0gRYaeoGeBPYSt89TIBpGb_DvgfPBmhV4sz0DYAErugX9DGvibMCvuNjj5EDIGgnQkIhP1cGqKunW6M08G2jF7lQTgcMCEmXjI59QtCKDYEOoT6zr3gXLgxxswDK8m08QG0MO1oeyZRqEWQIPj9dp6-9dva5lQkL7gE1eX3gAtOy8JxcNpg3Mj5Hr9nPz5bi1j518ov75D-HyrmvCl6ExTVeZGa_l6UHUdq-A%3D%3D&attredirects=0

It's a PDF for the Glow Plug Control Module Testing....

 

[DaveBen]

Look at the heavy feed wire and make sure it is connected and clean. Follow it back to the battery.

Dave

 

[toobsluver]

Well this is where I am at now. If anyone is interested, at this point it is more for documentation on this site. I ohm'd ALL the glow plugs at the connectors under the valve cover or the in gasket connector. They all ohm'd .9 off the passenger side battery and ohm'd at 2.7 to 2.9 on the driver side battery. Power is going to both plugs that connect to the glow plug control module (GPCM). Now, when the key is on, power is going to all of the glow plugs on the PASSENGER side but not the driver side. Based on the wiring diagram I have and the trouble shooting guide I have I think the GPCM is shot or something is wrong with the communication to the PCM or something is wrong with the PCM. I can't test the PCM because I don't have the tools to do so. I think. Wait, I'm still not done with this...

Lastly, after confirming that there is good continuity (ohms) to all the glow plugs, how come is there power going to the passenger side of the motor to all the glow plugs, yet I am still getting DTC codes for the passenger side of the motor. All my DTC codes are: P0678, 77, 76, 75, 74, 72. The even ending numbers are all the driver side. The odd are passenger side. From what I read. I could be wrong. So why am I still getting codes after trying to clear them a few times and I know there is power going to the whole passenger side of the motor. This is insane! I am going nuts.

Oh and one more thing, I checked continuity from both the black and green plugs that plug into the GPCM, and they too were still the same ohms. Nothing changed. So I now know that, the wiring going from the GPCM all the way to the glow plug itself is good. I have good wiring and good connections.

 

[RSG]

This is just a thought, probably off- base, but if the glow plug relay is a double pole (i.e. double switch) type with one pole for passenger side and the other for driver side, and if the passenger side pole is stuck open, that would result in your situation...that is, power is going to the input side, but not to both outputs. But...I don't know anything about that relay so I'm just guessing.

Another thought..check...is that when you test continuity, you are disconnecting the component from the circuit, right?

Good luck!

 

[toobsluver]

Yes it is disconnected when testing. Waiting for the new GPCM to get here.

 

[RSG]

Oh, sorry, I see now you have GPCM not GPR! Is this your 2nd new GPCM -- in earlier thread you wrote you bought one from Rock somebody or other and still got codes? Thanks for the nice diagrams I like that diagnostic listing.

 

[toobsluver]

Yeah, it will be my second GPCM. The only difference besides still getting the codes, this time I am going to test the wiring and see if I'm getting power to the driver side of the motor with this new GPCM. I didn't do that with the other one. I just plugged it in, cleared the codes and the codes came back.

 

[toobsluver]

Ok so this is where I am at now....

So I installed a new GPCM last night. Got power to all my glow plugs, cleared the codes and now I am still getting a P0677,76,75 and 72.

But they all are working. So I dunno whats going on now.

Everything ohm's at 1.0-.9 from the harness that plugs into the GPCM to the GP's themselves. I replaced all the plugs on the driver side of the motor even when they werent bad. Heck, my truck started up in 20 degree weather last night without it even being plugged in! It would never do that. It would take me like 15 minutes to get it started when it was that cold. This morning I am going to try it again.