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Totally SWAMPED
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109 Posts
Discussion Starter #1
i have been dealing with an ICP problem for some time and can't find the issue. here's the deal AE says i have 2800-3000psi at 28-30% duty cycle and mechanical gauge shows 600-1200psi. it will work 1 out of 10 times though i have tried 3 different pcm's and 5 different ICP sensor's including the one out of my 02 that is running fine. it's the same on all tunes including stock. any help or ideas this is starting to drive me nuts
 

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OverFuelingForYourPlesure
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1,609 Posts
sounds like a wireing issue, unhook the icp sensor and the connector at the pcm, then ohm out the sensor wires to make sure they dont have any extra resistance, if that is ok check for continuity between the the wires to make sure they arn't shorted together. then check to make sure they arn't shorted to ground, or any other wires in that harness.
if that all checks good you may need to load the wires, but start by just checking for resistance and shorts
a little bit of resistance can make a big differance.
 

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Totally SWAMPED
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109 Posts
Discussion Starter #3
i have already checked continuity and can't find a problem but i will check for resistance today and try loading the wires thanks for the help
 

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OverFuelingForYourPlesure
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1,609 Posts
be sure and look the connector at the sensor over real good that is where I generaly find the problem
 

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Headwind Magnet
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626 Posts
This is copied from a previous post. I didn't see you say you had the code, but you might find the info helpful.
Copied from an earlier post, this will get you through the pinpoint testing on the ICP / PCM side:


1280 indicates a possible ICP sensor circuit failure. You can check that by pulling the ICP harness and with the KOEO check the voltage between Pin B on the ICP harness and the battery ground. You should see 5 volts +- 0.5. IIRC Pin B is the Brown/White wire at the harness. If that checks then look at Pin B and Pin A, you should see the same voltage there. If you don't see the correct voltage you have an open circuit or short somewhere in that harness. If you see the correct voltage in both cases then you will need to move to the PCM connector. Since you probably don't have a breakout box for the PCM, you can just disconnect the PCM connector at the firewall and use that. Before you disconnect the PCM harness make sure you don't have the key in the ignition, the following tests are done with the keys removed. Look at the resistance between the following PCM pins and the ICP harness

PCM Pin 87 and ICP Harness Pin C = less than 5 ohms
PCM Pin 90 and ICP Harness Pin B = less than 5 ohms
PCM Pin 91 and ICP Harness Pin A = less than 5 ohms

If the wiring harness checks out above it could be either the ICP sensor itself or the PCM


Best,
Jim
 

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Totally SWAMPED
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109 Posts
Discussion Starter #6
well i checked the resistane it looks good
also with the key on pin B to battery and pin B to A they are with in .5 of each other there
is no check engine light and as i said in the first post i have tried 3 different PCM's 2 used and 1 reman from ford the truck acts the same with all of them also 4 New ICP sensor's plus the 1 out of my 02 i'm driving and have had no change
 

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OverFuelingForYourPlesure
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1,609 Posts
whenm watching the scanner, dose the icp pressure go to 0 with the engine off ?
 
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