When does the GPR come on?
Thread Starter
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Mountain Pass
Joined: Mar 2008
Posts: 199
Likes: 1
From: Uniontown KY
When does the GPR come on?
I installed a GPR LED on Sunday. I have been watching my Led when i turn on my truck. It seems to have a pattern of only coming on after my truck has sat for an hour or so or has cooled down a bit. It does work every time is is cooled down though. Is this normal or is it going out? I thought they came on every time you started the truck. Is there something different on the 01 trucks that could make it delay such as a temp switch or time delay?
Logistics Pro
Joined: Aug 2009
Posts: 3,609
Likes: 324
From: Arizona
My 02 is the same, it only comes on when cold. When warmed up and re started, it doesn't come on at all. Only if I let it sit for several hours will it come on. Also, it starts just fine every time.
I have the Stancor and the LED mods.
I have the Stancor and the LED mods.
Hotshot
Joined: Feb 2007
Posts: 10,499
Likes: 10
From: Sterling Heights,Mi
I installed a GPR LED on Sunday. I have been watching my Led when i turn on my truck. It seems to have a pattern of only coming on after my truck has sat for an hour or so or has cooled down a bit. It does work every time is is cooled down though. Is this normal or is it going out? I thought they came on every time you started the truck. Is there something different on the 01 trucks that could make it delay such as a temp switch or time delay?
Also on hot summer days the GPR LED will not come on.
Logistics Pro
Joined: Aug 2009
Posts: 3,609
Likes: 324
From: Arizona
Yes my factory glow plug light comes on every time, but the GPR only comes on when cold. So even though the factory glow plug indicator (which I guess is my WTS light) comes on every time, the glow plugs are not actually coming on every time, only when cold.
I always thought the WTS light came on every time to allow the fuel pressure to come up.
I always thought the WTS light came on every time to allow the fuel pressure to come up.
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
The GPR on-time is entirely a function of engine oil temp and baro. Basically there are two GPR maps that are programmed into the PCM, one for low altitude, and the other for high altitude. The PCM reads the baro to deterimine which map is used, then looks at oil temps to determine how long the GPR is to stay activated (if it's activated at all). Below are the maps for low altitude and high altitude. The X-axis is the engine oil temps, and the Y-axis is the time in seconds.
At low altitude, the GPR will not even activate until engine oil temps reach 55 degrees C (131 F). At high altitude, the GPR activates at warmer temps, turning on at 93 C (199 F). The maximum on-time is 120 seconds.
So that's why Chris would see his GPR activate all the time. Living at higher altitude in Colorado, the GPR activates at much warmer temps than at low altitude. At 199 F, that's a fully warm engine.
Anyway, hopefully this clarifies the GPR operation.
At low altitude, the GPR will not even activate until engine oil temps reach 55 degrees C (131 F). At high altitude, the GPR activates at warmer temps, turning on at 93 C (199 F). The maximum on-time is 120 seconds.
So that's why Chris would see his GPR activate all the time. Living at higher altitude in Colorado, the GPR activates at much warmer temps than at low altitude. At 199 F, that's a fully warm engine.
Anyway, hopefully this clarifies the GPR operation.
Thread Starter
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Mountain Pass
Joined: Mar 2008
Posts: 199
Likes: 1
From: Uniontown KY
Great info. It will be put up. Is there any different aperation with different PCMs or is this with all PCMs? I am running a PMT3.
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Post Fiend
Joined: Jun 2004
Posts: 9,293
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From: Parker, CO
The charts I posted are from a VDH2 PCM, but most of the others are the same, including the PMT3. The only ones that I don't know for sure are the Cali models and the Excursions that have the GPCM. That's a different animal. Cody might have those files.
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Lead Driver
Joined: Jan 2007
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From: Kiowa CO
Thanks for the clarification, Curtis. I was thinking I was going nuts by seeing my LED come on all the time. It's been a while since I've taken the truck to lower elevations to see the behavior of the LED change. Good info.
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
Depends on the year. Earlier Superduties had a baro sensor under the dash above the accelerator pedal. Later, Ford relocated the sensor inside the PCM.
