What the heck is going on....... .05 ref volts ICP
- Thread starter Cgrigson1
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Cgrigson1
New member
Oh and I was getting zero codes on my scangauge will it was running earlier.
Air testing at the icp will test the entire system. Pull the inlet off to the turbo, and you should be able to hear into the crankcase vent for a leak on the drivers side, and oil cap on the passenger. You may have to cycle the ipr a few times to purge all the oil out of the rails to hear a leak. On top of the pump with a rubber tipped air nozzle works too, its just a bit more work getting to it. If you suspect the pump may have a blown out seal after esting at the icp, i would pump air directly into e discharge port on the pump to make sure.
Cgrigson1
New member
Man I haven't a clue why this damn thing is running so bad. When it's cold and I start it I can rev it up fine and it doesn't sound that bad. I need to drive it I guess but started it up warm today and was very very slow to respond to the pedal but would and when I put it in reverse to move it No response at the pedal. Still not currect voltage reading on the ICP. I'm at a complete loss. Seems like the damn thing does something different every time I try to start it. It's cold now and I'm going to try to start it again and it's definitely not building pressure quickly it takes a good 6-8 seconds to build enough to start and cold you saw my IPR and ICP readings which are normal and when it gets warmed up it starts to surge and sound like ****! Do you know these symptoms?
Cgrigson1
New member
When i did the air leak test at the ICP my compressor built up pressure and shut off for several minutes but the IPR was closed right cuz engine wasn't running and I don't know how to cycle it. My scangauge can't control it as far as I know. I heard absolutely zero leaks and like I said my compressor wouldn't have shut off had there been a leak?
Your ipr would have been open with the engine off. You need to apply 12v to the ipr to close it. A 7.3 injector pigtail and some long ass wire will work. Dont apply voltage any longer than 2 minutes, otherwise the ipr can be damaged. You could have a pump chitting the bed, they have similar symptoms to what youre describing.
Also double check your oil and filter if you havent alreday.
Also double check your oil and filter if you havent alreday.
Cgrigson1
New member
Yeah oil and filter are good. I feel like I might be changing out the pump starting tomorrow I have a buddy with an Acct and can get it for $750 but that still doesn't solve my low ICP voltage issue which I will super concentrate on tomorrow. Gonna ck voltage at the pin on the CPU first thing which I should be done with by 9:30am. I'll send my result
Cgrigson1
New member
Still .01 on scangauge. Just started it cold ICP went from 5 to over a thousand in two seconds hit the pedal and very slow to build up response but had ICP up to over 3000 within seconds. Reved up ICP voltage showed .08 on my gauge. Hell if I set it on fire I would maybe get. 1/4 of what I have in it. Just spent a grand on tires not two months ago. It's a 2wd but has a six inch lift and running 35's plus it has a sick stereo system and motor rebuilt 35k miles ago and the dude had to for four freaking months and charged me $6000. I gotta get this figured out within the next week and have the time to get on it and stay on it. ICP over 3000 just now! Still very sluggish to rev up
Cgrigson1
New member
Throttle response very slow
Cgrigson1
New member
Nice truck man.
Re reading thru everything, you have a manually measured 5.0v at the vref pin on the icp. Is this to battery ground, or signal return, which would be the top right pin on the icp? I am leaning towards a shorted sensor or harness somewhere pulling your vref down. Did you unplug the app (throttle pedal), and baro? The baro is behind the drivers knee panel, it will be a 3 wire sensor that looks like it has a cap on the end of it.
You could also have an open signal wire between the pcm and the single pin on the icp. Start by checking all 3 pins for short to ground, and each other. Continuity to both ground and each other should be open circuit. Make sure this is done with the pcm unplugged. Also double check that all the wires have good continuity to the pcm. Were talking like .5 ohms or less here.
Re reading thru everything, you have a manually measured 5.0v at the vref pin on the icp. Is this to battery ground, or signal return, which would be the top right pin on the icp? I am leaning towards a shorted sensor or harness somewhere pulling your vref down. Did you unplug the app (throttle pedal), and baro? The baro is behind the drivers knee panel, it will be a 3 wire sensor that looks like it has a cap on the end of it.
You could also have an open signal wire between the pcm and the single pin on the icp. Start by checking all 3 pins for short to ground, and each other. Continuity to both ground and each other should be open circuit. Make sure this is done with the pcm unplugged. Also double check that all the wires have good continuity to the pcm. Were talking like .5 ohms or less here.
Lets make sure here too, when they re built your engine, they didnt get harnesses swapped by any chance did they? Later harnesses, 05-07, have different pin outs at the pcm, and possibly other places as well. Best way to check this is to see if the throttle plate connectors are still there.
Cgrigson1
New member
Hey man thanks so much for your help! So cool of you. Responding respectfully to your last two bits of advice best I can.
I manually measured 5v at the left top pin on ICP pig neg on the battery. I unplugged the throttle pedal plug and refv was still showing .01 on my scangauge. My plan tomorrow is to try and find the Baro you spoke of. Knee panel is left side panel under my feet I'm assuming.
You mentioned I may have an open signal wire between pcm and which single pin on the icp? We checked for continuity between all three pins and the relative pins at CPU based on the diagram another guy sent me which I posted on our thread and everyting checked out with a test light and a long piece of wire I have for doing so.
I'm not sure what you mean by ck all 3 pins for short to ground. I have a digital volt meter with a lot of fancy signals and signs and I may have to pull up a manual that shows me how to read ohms on a continuity ck.
So I started it again today and saw 1200 psi at idle ICP and hammered down on the pedal and was slow slow to react and when she did rev up saw over 3000icp. Tells me my pump isn't weak or bad nor is there a leak at that kind of build up of pressure. Goofy thing is when I put it in reverse to try to go drive it I get Zero throttle response.
The base engine is great and I just can't afford to shop it to a shop and again,super appreciate your advice especially this time of year
Clay
I manually measured 5v at the left top pin on ICP pig neg on the battery. I unplugged the throttle pedal plug and refv was still showing .01 on my scangauge. My plan tomorrow is to try and find the Baro you spoke of. Knee panel is left side panel under my feet I'm assuming.
You mentioned I may have an open signal wire between pcm and which single pin on the icp? We checked for continuity between all three pins and the relative pins at CPU based on the diagram another guy sent me which I posted on our thread and everyting checked out with a test light and a long piece of wire I have for doing so.
I'm not sure what you mean by ck all 3 pins for short to ground. I have a digital volt meter with a lot of fancy signals and signs and I may have to pull up a manual that shows me how to read ohms on a continuity ck.
So I started it again today and saw 1200 psi at idle ICP and hammered down on the pedal and was slow slow to react and when she did rev up saw over 3000icp. Tells me my pump isn't weak or bad nor is there a leak at that kind of build up of pressure. Goofy thing is when I put it in reverse to try to go drive it I get Zero throttle response.
The base engine is great and I just can't afford to shop it to a shop and again,super appreciate your advice especially this time of year
Clay
Cgrigson1
New member
The engine was rebuilt over two years ago and it ran perfectly up until a month ago
lenzhotrod
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What happens if you leave the ICP unplugged?
For checking short to ground, unplug the pcm and measure ohms to the battery negative. Ohms is the upside down horseshoe looking symbol. You should have over 10k ohms to ground on all 3 pins. Also, do the same check, but to each pin in the icp, not to battery negative.
As for you not condemning the pump because it builds over 3000 psi when cold, doesnt mean its good, it could be internally grenading, and only act up warm at this point due to the aluminum expanding with the heat, but i will agree the wiring issue needs figured out first.
With your scan gauge, check what your voltages are on all the sensors i mentioned earlier, map, baro, ebp, app, egr, egr throttle plate, and icp. Make sure you have good voltage to all of these, computer wise, as that will rule out certain things, such as the computer, being bad. And your bknee panel, is that panel that covers the fuse box withthe 4 quick turn screws in it. The baro should be christmas treed to part of the dash or steering column.
No worries on the help man, thats what we're here for.
As for you not condemning the pump because it builds over 3000 psi when cold, doesnt mean its good, it could be internally grenading, and only act up warm at this point due to the aluminum expanding with the heat, but i will agree the wiring issue needs figured out first.
With your scan gauge, check what your voltages are on all the sensors i mentioned earlier, map, baro, ebp, app, egr, egr throttle plate, and icp. Make sure you have good voltage to all of these, computer wise, as that will rule out certain things, such as the computer, being bad. And your bknee panel, is that panel that covers the fuse box withthe 4 quick turn screws in it. The baro should be christmas treed to part of the dash or steering column.
No worries on the help man, thats what we're here for.
Last edited:
Cgrigson1
New member
No change man with ICP unplugged. I'll start checking on these sensor ohms and ground and voltage. I bought a Chilton book and was a complete waste of money. Will my alldatadiy program have the correct voltage for these other sensors you listed? I'm not sure what to look for. Its raining today here so haven't been able to get on it like I had hoped.
thanks
thanks
webb06
Active member
Sounds to me like you need to do the air test again and make sure you don't have any leaks. Since you don't have a way to close the ipr valve, if you turn the key on before you connect the air hose the ipr will likely be closed enough so you can hear any leaks. Leave the air hose connected for at least 2-3 minutes to get the oil purged out of the rails.
Side note, does the dash gauge register that you have oil pressure when it's running?
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Side note, does the dash gauge register that you have oil pressure when it's running?
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webb06
Active member
You also mentioned that it ran okay coming back from the shop you had look at it? Before you replaced the ipr and had the oil rail off?
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