I have a 2000 f250 7.3, my GPCM is not on the valve cover. My ford certified mechanic couldn't find it either. It's giving 2 codes: open circuit ECM, and open circuit GPCM. He also had never seen the metal "strap" that goes over the glow plug terminal on the relay. Does anyone else have this set up, and please let me know where the GPCM is located. I tried to attach a picture, but it wouldn't. Thank you

 

You do not have a GPCM, you have a Glow Plug Relay Shunt.

 

How long has your Ford certified mechanic been working on diesels? A word of advice, mechanic and certified diesel tech are two very different things. A good diesel tech will fix your problems. A mechanic will only follow the charts and throw parts at it.

From what you're describing, someone has removed the GPCM that came standard on the 2000 model CA emissions equipped trucks and installed a GPR with a splitter off an early 99 model CA emission truck because it was cheaper. As you are aware, this does not work in fooling the computer that everything is working.

Since the 2000 model CA emissions trucks came with a GPCM, I'd be more worried about what happened to the wiring and plugs and how they tried to make those work with the GPR. If your 2000 truck was not a CA emissions equipped vehicle, then you never had a GPCM or the wiring.

If you had a picture of under your hood of the GPR / GPCM area, we could tell you a lot more.

 

It looks exactly like the picture that was just posted by someone else. It is a federal (non ca) model. If I don't have one, or the plugs and harness, what do I do next to get them to work? He ohm tested them and said they test like they're new .5 ohms, all 8 of them. The truck has 200,005 miles on it. Obviously the glow plugs have never worked if they're still reading good after that long. Very discouraging as this is my 8th winter in Idaho, and I cant always get it plugged in.

 

Let me try this again...the "mechanic" said its a federal model, but IS originally from ca. I purchased OT from my father in law who lives in so cal. So how do I tell which model it is?

 

I believe the ca trucks have a sticker somewhere on them stating they are ca trucks. I don't know if the sticker would still be there now. The thing I'd check is the wiring coming off the GPR. Trace it back and see where it goes. You should be able to tell if someone tried to splice wires from it into GPCM wiring since it won't look factory.

There's no reason glow plugs can't last that long. Mine lasted over 300,000 miles and still ohmed out fine. Are you sure the glow plugs are not working properly? Have you tested the GPR that you have on there with a volt meter to see if you have voltage coming out of it going to the glow plugs after the key is turned on? (one large post always shows 12 volts or so, the other large post only shows 12 volts after the key is turned on for up to 2 mins.)

 

There is no power going to the drivers side post, and the relay has been replaced twice.

 

It sounds as though the PCM is bad or it originally had a GPCM and was removed, or the PCM was swapped with a CA PCM?

Either way, I believe it is a light blue wire that goes to the coil from the PCM giving the coil it's ground to close. You could as some have done, wire it to a switch providing ground to the coil and manually activating it.

 

I'm desperate at this point. I can't keep getting stranded when I can't plug it in, and all that cold cranking is hell on the engine. Is there a link to a thread (hopefully with pictures) on how to do the switch?

 

I believe too that there is a fusible link to protect the PCM on the blue or purple wire for the coil? You might check for continuity. I will try to find a link to a manual GPR.

 

Here is a link for a manual switch https://www.ford-trucks.com/forums/1...o-the-gpr.html

No pics, but if you get the idea it's pretty simple, small post on the GPR wired through a switch with the other side of the switch going to ground.

 

Here's the one I was looking for got some pics for you too.

https://www.ford-trucks.com/forums/8...ss-switch.html

 

First things first. Are you having a hard start when cold or what is the problem. You sound like you are trying to troubleshoot the system, but unsure of what you are looking for. The GPR is a pretty simple system to checkout. It is easier to have two people when doing the troubleshooting. One under the hood and one at the key. The two large posts should have power once the key is turned on with the engine cold. Oil temperature is what triggers the GPR to work. The PCM determines the time they remain on based on the oil temperature input.

You have 4 posts, Two large and two small. One of the large posts and one small one should always have 12V on them. The post with the shunt should only be energized the first minute or two (depending on oil temp). The back small post is the ground input. You will notice when it is not grounded (GPR off) it will have 12V applied. This is because it is not grounded so it appears like it has a 12V feed. It is no different than hooking a light bulb up to a power source and reading voltage off of the ground side.

Do a thourogh checkout of your GPR system and manually ground the back post. See if you hear the GPR cycling or see if voltage goes to the other large post. It is not all that uncommon for the GPR to fail multiple times. Especially if it was replaced with a cheaper quality version.

 

Thank you very much for your help. I see no other options, since I don't have the plugs there from the harness to put a GPCM in.

 

Yes it is hard starting. It will not start off the temp is below 32 unless it had been plugged in.