CPIPSD is correct here, as my truck is a Wisconsin truck...no California emissions. What drives the GPR then? Is it the GEM Module?

 

sorry about that giving you the wrong info there, my father has an excursion that I recently did a little work on so it was fresh in my head, and just typing it in google images probably just gave me a picture of an excursion. it's been a while

The PCM controls the GPR in your case

And just FYI, the state you bought the vehicle in does not matter (unless you live in California). California emissions is just a standard (a more strict set of parameters), you can get a California emissions vehicle ordered and delivered to any of the 50 states. For example; a friend of mine bought a 95' F350 PSD from a company on the eastern side of CT. He was only the second owner, and the company bought the truck brand new. After looking at the truck for him after he bought it, I found the "Catalyst" sticker on the radiator support which says in bold print "California Emissions Equipped". -coming from a CT emissions inspector

 

No sweat DieselDanBoy, I can certainly understand the mixup. I looked and saw nothing there :P I'm on a witch hunt now, post back later.

 

Although I'm still confident it's a relay control circuit issue

 

Ran into this a time or two in my shop. First time it was the PCM that was faulty, second time it was wiring in the main harness leading up to the 42 pin connector not actually the engine harness.

Quick test is to pull the small wires off (so that one doesnt power the other thru the relay) and see if both have power when the key is turned on. If so then powers coming from the PCM and wiring good if not onto testing the harness

Find a good wiring diagram and then test resistance in the two activation wires from at the Glow Plug Relay all the way to the associate pin at the PCM plug at the firewall (pull the plug DONT PROBE!) is how I test them. If both wires are good then you're only left with a fault bus circuit in the PCM or a magical gremlin

 

Nice truck smokie, welcome too db and do you have any good schematics? or know where to get em?

 

New to posting so hope this works. Im attaching (or hoping to) acouple of my diagrams ones for pickups ones for excursion. Cant seem to find any of my info on the pin layout on the connectors tho. Ill keep looking

 

Very awesome Thanks for the info.

Now, here's what I've got.

Key off, no voltage at the GPR except for the 1 large terminal (Direct to battery).

Key on, voltage at same large terminal, and voltage at the small terminal toward front of truck (red wire), but no voltage at the other large terminal. Voltage at the other small terminal as well, but no activity on the relay. The other wire is orange, and when I ground that terminal (with orange wire off), the relay operates. So that leads me back to looking at the 42 pin connector for fault there or the wire itself (between the relay to the 42 pin connector). Is that connector on the driver side valve cover?

Thanks for the diagram as well. I love having an arsenal of info.

 

the orange wire is ground. maybe the ground is just bad?

 

PCM main hot comes to one small wire so it'll always be hot, cant remember which one. Other one is hot when the PCM doesnt want glow plugs then the PCM sends ground to activate. Did you unhook the wires from the relay when youre testing them?? IF not then one wire can power the other thru the relay coil and you dont learn anything from testing.

If both wires (tested while unhooked from relay) have power youre left with a bad PCM which happens or I think the oil temp sensor might play a roll in deciding if the glow plugs kick on or not but dont hold me to that.

Got a buddy that wouldn't mind lending you a PCM for a quick test??

-Jordan