GPR problem
Thread Starter
|
Posting Guru
Joined: Aug 2002
Posts: 1,729
Likes: 2
GPR problem
Working on a friends 99, problem is the GPR isn't engaging. The relay works when bypassed or my AE is hooked up and is tested that way.
Once the key is turned on it has 12v to the coil post on the relay but no ground. Jumper a ground to the other post and the relay closes and powers. But that brings another problem the 12v doesn't cycle off (with or without the ground jumper attached).
Could their be a problem with the PCM not sending the ground to the GPR? And in turn keeping 12v supplied at all times? The only codes were for a GPR fault (assuming from the cold starts stumbles). Their was a code for the IAT having a high input, looking at live feed it's (possible default) of 59*
Any ideas? Thanks
Once the key is turned on it has 12v to the coil post on the relay but no ground. Jumper a ground to the other post and the relay closes and powers. But that brings another problem the 12v doesn't cycle off (with or without the ground jumper attached).
Could their be a problem with the PCM not sending the ground to the GPR? And in turn keeping 12v supplied at all times? The only codes were for a GPR fault (assuming from the cold starts stumbles). Their was a code for the IAT having a high input, looking at live feed it's (possible default) of 59*
Any ideas? Thanks
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
I don't think you'll find a code for the GPR unless it's a CA truck (spreader bar on GPR). Is the 12v all the time on the 2nd large post on the GPR, or just the other small post? It's normal for the little posts to read 12v, but if the large output post sending power to the glow plugs reads 12v all the time, your friend will probably need new glow plugs.
No ground signal could be a PCM issue, a wiring issue, or maybe just a bad GPR. Have you checked for the ground signal with the wire disconnected from the GPR? If you reach the point you suspect a PCM problem, keep in mind you can just wire up a push button to activate the GPR for a lot less than a new PCM.
No ground signal could be a PCM issue, a wiring issue, or maybe just a bad GPR. Have you checked for the ground signal with the wire disconnected from the GPR? If you reach the point you suspect a PCM problem, keep in mind you can just wire up a push button to activate the GPR for a lot less than a new PCM.
Hotshot
Joined: Jan 2008
Posts: 13,144
Likes: 11
From: Rochdale MA
I don't think you'll find a code for the GPR unless it's a CA truck (spreader bar on GPR). Is the 12v all the time on the 2nd large post on the GPR, or just the other small post? It's normal for the little posts to read 12v, but if the large output post sending power to the glow plugs reads 12v all the time, your friend will probably need new glow plugs.
No ground signal could be a PCM issue, a wiring issue, or maybe just a bad GPR. Have you checked for the ground signal with the wire disconnected from the GPR? If you reach the point you suspect a PCM problem, keep in mind you can just wire up a push button to activate the GPR for a lot less than a new PCM.
No ground signal could be a PCM issue, a wiring issue, or maybe just a bad GPR. Have you checked for the ground signal with the wire disconnected from the GPR? If you reach the point you suspect a PCM problem, keep in mind you can just wire up a push button to activate the GPR for a lot less than a new PCM.
Thread Starter
|
Posting Guru
Joined: Aug 2002
Posts: 1,729
Likes: 2
The constant 12v is on the little post. The ground to the other little post is there but doesn't seem to be a very good ground (once the 12v reaches the other little post it goes straight thru to make 12v on both little posts). I was leaning toward the PCM since the switching 12v doesn't switch off.
The push button was the first thing that came to mind once we started talking prices of PCM's! LoL
The push button was the first thing that came to mind once we started talking prices of PCM's! LoL
Hotshot
Joined: Jul 2003
Posts: 12,177
Likes: 40
From: Newport, WA
The constant 12v is on the little post. The ground to the other little post is there but doesn't seem to be a very good ground (once the 12v reaches the other little post it goes straight thru to make 12v on both little posts). I was leaning toward the PCM since the switching 12v doesn't switch off.
The push button was the first thing that came to mind once we started talking prices of PCM's! LoL
The push button was the first thing that came to mind once we started talking prices of PCM's! LoL
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
I believe the little post is 12v with the key on. So as long as the key is on, you'll see 12v there. It's the ground signal that trips the relay and sends the voltage to the glow plugs.
Trending Topics
Thread Starter
|
Posting Guru
Joined: Aug 2002
Posts: 1,729
Likes: 2
Ok, I don't have another SD to check it on. I checked 97 and it cycles the 12v off after 15 sec or so. Does the PCM control (which ever is switched ground or 12v) just off of programing or does it take sensor readings to cycle the GPR?
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
PCM provides the ground signal only. You can verify this with a multi-meter watching the output volts on the 2nd large post. Remove the small wire with 12v and you won't see any power out of the GPR. Add a ground signal to the small post and you'll see the 12v go to the glow plugs.