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THE SILVER BULLET
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Discussion Starter · #1 ·
I am posting this question just to enhance my and others knowledge about the operation of the ICP system.

I have an 03 6.0 which has the ICP sensor located under the turbo and is a pain to change. I have changed it twice already, due to oil leaks. About 2 years ago it started acting up again, but instead of oil leak it would just start reading erratically and causing the engine to rev and/or stall unexpectantly. Due to the drive-ability/safety issues and difficulty/expense to change I decided to disconnect the ICP sensor and run off the tables.
I was surprised that the truck ran so well and have not ever messed with it since.

It has been disconnected for about 2 years now and I have not had any problems or fuel mileage loss.

So my question is, What is the exact purpose of the ICP sensor and what is effected by it being disconnected??


Thanks
 

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Heres a description below of the ICP sensor out of the 6L bible. It's nice to know you can run it unplugged without any percieved consequeces so far. But for me, I would want it functioning. In fact, ICP is one of my main monitored readings I use on my ScanGauge2. IPR and FICM timing are both based off inputs to the pcm from the ICP sensor. I have changed mine once myself and once when it was still under warranty. Myself, it only took a short while during my lunch break. With an open end 1-1/16" wrench, with a cut down handle, and a hoist, it's a quick and fairly easy task.

http://www.backglass.org/duncan/ps60_manual/ps60_061.jpg

Harry
 

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THE SILVER BULLET
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Discussion Starter · #3 ·
Your type reply and one reason why I made this post. 2 years ago when I was researching if the ICP sensor could be unplugged turned up two responses to the question.
1. Sure it can and the PCM will revert to "safe" run tables that are there so the engine will run in the event of ICP sensor failure.
and
2. No don't do it, it will cause engine damage..

When asked how it could cause engine damage, that is where the story geys really muddy and the answer was usually something like "I wouldn't do it on my truck" or a buddy of a friend of a cousin tried it and he blew an engine I heard,,," But no one could ever produce any real evidence of engine damage caused from the ICP sensor being unplugged.

So I tried it and I have not had any issues what so ever. And I tow a 40 foot 5th wheel and run an SCT race tune 100% of the time.

I feel that I do not have the power on tap that I would with the ICP sensor operational due to running off the PCM run tables which I am sure are purposely on the low side, but I have plenty of power, way more than stock..

and to clarify, I am not trying start an argument, but merely trying to understand why or how unplugging the ICP would cause engine damage that is frequently stated and what would the damage be?
 

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I'll add my 2 cents..

I relocated my ICP to on top of the engine using hydraulic tubing. It was a fun project and has come in handy. Search for my posts about my adventures under the hood.

I'm no expert but this is what I have observed. The ICP is the input to the PCM for controlling the injection pressure. The PCM uses the information to fine tune the pressure by adjusting the IPR. Without an ICP the PCM can only guess as to what the pressure is and therefore your injectors may not have the ideal pressure to operate. This is sometimes refered to as "Limp Home Mode".

I was experimenting with my AE tool and while at idle I commanded the IPR to 100%. I watched the ICP pressure sky rocket and the engine about died due to the sudden increase in work the HPOP was asked to do. So without knowing the exact details, the PCM commands the IPR to regulate the pressure at different levels for differant power requirements. Running without an ICP may not cause any damage but also may not allow your engine to operate in its most efficent manner.

You mentioned that you dont have all the power while the ICP is disconnected. I have observed the ICP pressure with a gauge while my ICP was disconnected, and at heavy throttle, the pressure doesn't build to what it does when the ICP is functioning. Lack of ICP pressure causes poor injection and loss of power.
 

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THE SILVER BULLET
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Discussion Starter · #5 · (Edited)
I relocated my ICP to on top of the engine using hydraulic tubing. It was a fun project and has come in handy.
That is actually what I will do the next time I have to R&R the turbo. At this point it just has not been worth the effort just to replace the ICP sensor.

But again I have wondered why people always state that engine damage will occur if you continue to drive with the ICP sensor unplugged.
The only thing that I could think of would be if the IPR malfunctioned, that could cause engine damage. But if the IPR malfunctioned, it would not matter if ICP was plugged in or not, because the PCM could no longer control a malfunctioning IPR anyways...at least that is the conclusion I have come to. If I am wrong, please educate me.
I also feel that a Plugged in "Malfunctioning" ICP sensor would be far worse than an unplugged icp sensor.
 

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Yes, a malfunctioning/erratic reading ICP sensor will cause driveability issues, no doubt about that. The default table that the PCM reverts to when the ICP is unplugged is probably fine to run as you have proven that, but not ideal. Remember, the PCM commands the IPR, based off inputs from the ICP, to make hi-pressure oil calculations and adjustments, or in your case, reverts to a pre-programmed fault condition table. Which could also effect other engine control parameters. But like I said before, for myself, I would want my ICP input fully functioning. But if it works for you, then thats what really counts. Your IPR is basing its operation from a pre-set table that will allow the engine to function ok, and you have proven that in the last 2yrs. And I am glad you have shared this info, as its always good to know that one can unplug the ICP if it malfunctions. I would have to assume your check engine light is on all the time, am I correct?

Harry
 

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THE SILVER BULLET
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Discussion Starter · #7 ·
Yes, a malfunctioning/erratic reading ICP sensor will cause driveability issues, no doubt about that. The default table that the PCM reverts to when the ICP is unplugged is probably fine to run as you have proven that, but not ideal. Remember, the PCM commands the IPR, based off inputs from the ICP, to make hi-pressure oil calculations and adjustments, or in your case, reverts to a pre-programmed fault condition table. Which could also effect other engine control parameters. But like I said before, for myself, I would want my ICP input fully functioning. But if it works for you, then thats what really counts. Your IPR is basing its operation from a pre-set table that will allow the engine to function ok, and you have proven that in the last 2yrs. And I am glad you have shared this info, as its always good to know that one can unplug the ICP if it malfunctions. I would have to assume your check engine light is on all the time, am I correct?

Harry
Yes the check engine light stays on.

This is where things could get ugly but..here goes.

I have the SCT proracer program and can write my own tune files. So I can turn the light off if I wanted to and I could modify the ICP tables to bump up the "Unplugged" power. But I have not been that brave/stupid..yet..lol

But I would like to dispel the myth that ones engine is going to be damaged by unplugging the sensor.

Will it cause a loss in power: Yes

Is it something to do for any performance increase: NO

Is it safer to run unplugged Vs. continuing to run a malfunctioning ICP sensor: I believe so.

Will you have a check engine light on: Yes, but if you are experiencing a failing ICP sensor, it will be on anyways.

And to clarify one more small thing that I did with my situation:
I did not crawl under the truck and unplug the sensor. I actual cut the signal wire at the pcm and made a connector there so I could easily plug/unplug from under the hood. And again, I will eventually replace the ICP sensor, (already have one on hand) when I have enough of a reason to remove the turbo. Then I will figure a way to remote mount the ICP sensor so that it is easily accessible and to get it away from the turbo heat, since I suspect that is what actually causes the ICP sensors to fail.
 

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Rick, I have to disagree with you about being "safer" to run with the ICP disconnected. I don't think that one way or the other is safer. I also dont think that engine damage could occur either way. The worst case is the pressure goes to 4000psi and the pressure relief in the IPR relieves pressure back to the oil pan. The entire HPOP system can sustain 4000psi because that is what it is designed to do under heavy throttle. The other extreme case is lack of power or not running at all, which cant cause damage but is annoying.

You mentioned that you have a connector at the PCM to disconnect the ICP. I took that idea one step further and installed a switch in the ICP circuit. I can flip the switch to disconnect the ICP any time I want. The switch served its purpose and I haven't used it in a long time. The most useful thing I did was installed a 0-5000psi pressure gauge in the ICP line.

One problem I had that I thought was a faulty ICP turned out to be a frayed wire in the wire harness. As it turned out, the 5 volt refrence to the ICP was intermitantly shorting to the ground wire and the PCM was reporting this as an ICP failure. The PCM would also sometimes hickup and the engine would quit. The ICP sensor itself was always working just fine. I found the short by shear dumb luck while examining the wiring harness. The problem was caused by the dealer making a bad splice when they replaced the ICP because it was blowing oil all over the place (what a mess!) The bad splice is now in my "museum" of things gone bad. This is my first reason never to go to a dealer again and why I started "fixinitmyself".

The lessons learned here is always test, verify and then repair the problem. (I think it was Lenzhotrod that coined that phrase, Thanks Len!) Dont just guess or blindly accept what the computers are telling you.
 

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THE SILVER BULLET
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Discussion Starter · #9 ·
Rick, I have to disagree with you about being "safer" to run with the ICP disconnected. I don't think that one way or the other is safer. I also dont think that engine damage could occur either way. The worst case is the pressure goes to 4000psi and the pressure relief in the IPR relieves pressure back to the oil pan. The entire HPOP system can sustain 4000psi because that is what it is designed to do under heavy throttle. The other extreme case is lack of power or not running at all, which cant cause damage but is annoying.

You mentioned that you have a connector at the PCM to disconnect the ICP. I took that idea one step further and installed a switch in the ICP circuit. I can flip the switch to disconnect the ICP any time I want. The switch served its purpose and I haven't used it in a long time. The most useful thing I did was installed a 0-5000psi pressure gauge in the ICP line.

One problem I had that I thought was a faulty ICP turned out to be a frayed wire in the wire harness. As it turned out, the 5 volt refrence to the ICP was intermitantly shorting to the ground wire and the PCM was reporting this as an ICP failure. The PCM would also sometimes hickup and the engine would quit. The ICP sensor itself was always working just fine. I found the short by shear dumb luck while examining the wiring harness. The problem was caused by the dealer making a bad splice when they replaced the ICP because it was blowing oil all over the place (what a mess!) The bad splice is now in my "museum" of things gone bad. This is my first reason never to go to a dealer again and why I started "fixinitmyself".

The lessons learned here is always test, verify and then repair the problem. (I think it was Lenzhotrod that coined that phrase, Thanks Len!) Dont just guess or blindly accept what the computers are telling you.
The reason I would say it is safer, is due to how my truck was reacting to the erratic ICP signal. It would unexpectedly take off if at a stop light etc.. and if I did not have my foot on the brake hard, it could potentially launch into a car in front of me. It was bad enough that I would not let anyone else drive my truck.

I do agree that my issue maybe harness related also. I will eventually find out when I am back on top of the engine..but hopefully no time soon..lol
 

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Wow, Sounds like you have a bigger issue than a flakey ICP sensor. You seemed to have the intermitant problem isolated by your connector at the PCM. I hate to think that you may have a similar problem like the run away Toyotas. I have never heard of a Ford having the sudden run away problem. I'm not saying that you do for sure but since these engines are 100% "drive-by-wire" anything is possible.

Keep after it and you will eventually find the source of the problem.
 

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THE SILVER BULLET
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Discussion Starter · #11 ·
Wow, Sounds like you have a bigger issue than a flakey ICP sensor. You seemed to have the intermitant problem isolated by your connector at the PCM. I hate to think that you may have a similar problem like the run away Toyotas. I have never heard of a Ford having the sudden run away problem. I'm not saying that you do for sure but since these engines are 100% "drive-by-wire" anything is possible.

Keep after it and you will eventually find the source of the problem.
Nah, it wasn't anything like a runaway throttle, but the change from a low idle to a higher idle unexpectedly in a diesel is enough to make one keep your foot firmly on the brake..lol
 

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Surging idle is one of the symptoms that can occur from a weak/faulty ICP sensor. I agree, it's in a bad spot on our 03' yr models, and heat is no doubt the greatest contributing factor to the repeated ICP failures on these early models, hence the later models it was moved away from the turbo. The whole high pressure oil thing is overly complex in order to fire some injectors in my opinion. Too many variables that can affect injection operations, but it is what it is, and any new little tricks to make life easier are always welcome in my book.
So the answer to your question in a nutshell is......one can run a 6L with no ICP input and possibly have a better running truck than one with a malfunctioning ICP sensor, but it won't run as good as a truck will with a good working ICP sensor. And it won't hurt the engine to run it this way.

Harry
 

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THE SILVER BULLET
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Discussion Starter · #13 ·
Surging idle is one of the symptoms that can occur from a weak/faulty ICP sensor. I agree, it's in a bad spot on our 03' yr models, and heat is no doubt the greatest contributing factor to the repeated ICP failures on these early models, hence the later models it was moved away from the turbo. The whole high pressure oil thing is overly complex in order to fire some injectors in my opinion. Too many variables that can affect injection operations, but it is what it is, and any new little tricks to make life easier are always welcome in my book.
So the answer to your question in a nutshell is......one can run a 6L with no ICP input and possibly have a better running truck than one with a malfunctioning ICP sensor, but it won't run as good as a truck will with a good working ICP sensor. And it won't hurt the engine to run it this way.

Harry
Hey Harry, off topic, but, how do you like that Powermax Turbo?
 

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Would never go back to stock. Custom tuning is a must to get it dialed in, but once it is tuned right, it rocks. If you want a long read on it, go to this thread that I started back when I installed it,
http://www.thedieselgarage.com/forums/showthread.php?t=100735

In a nutshell, it has massive midrange capabilities, flows more air, and will support more fuel. It tows well when tuned right. Spool up is a bit slower than a stocker off the line, but spools quickly once it gets going, and driving down the road is where it really shines.

Harry
 

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I'll add my 2 cents.. I relocated my ICP to on top of the engine using hydraulic tubing. It was a fun project and has come in handy. Search for my posts about my adventures under the hood. I'm no expert but this is what I have observed. The ICP is the input to the PCM for controlling the injection pressure. The PCM uses the information to fine tune the pressure by adjusting the IPR. Without an ICP the PCM can only guess as to what the pressure is and therefore your injectors may not have the ideal pressure to operate. This is sometimes refered to as "Limp Home Mode". I was experimenting with my AE tool and while at idle I commanded the IPR to 100%. I watched the ICP pressure sky rocket and the engine about died due to the sudden increase in work the HPOP was asked to do. So without knowing the exact details, the PCM commands the IPR to regulate the pressure at different levels for differant power requirements. Running without an ICP may not cause any damage but also may not allow your engine to operate in its most efficent manner. You mentioned that you dont have all the power while the ICP is disconnected. I have observed the ICP pressure with a gauge while my ICP was disconnected, and at heavy throttle, the pressure doesn't build to what it does when the ICP is functioning. Lack of ICP pressure causes poor injection and loss of power.
Very interested in the relocating of the sensor, please help
 
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