computer will not give codes help plz

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Jan 15, 2014 | 01:10 AM

E-5-USMC

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computer will not give codes help plz

Hi guy im new here so please bare with me on this ok that said i have an 86 f150 302 EFI im the secound owner got it from my dad it sat most of the last few years was running great cold snap came in an now it runs well kinda runs started out real high idel 1500 or so and stays there hot or cold! now has no start prob but i can start with starter fluid and it will stay running and run great but have to use fluid everytime to start relay is good i checked fuel pump works all three do i checked!!! i have not checked FPR as i have nothing to test it with yet! also i tried to pull computer codes with test light can not seem to get it to work yes i am sure i did it right i have read enough post here to know i have!!! when i turn key on for KOEO test computer does nothing no relays click nothing can someone help with this please where should i go from here?

Last edited by E-5-USMC; Jan 15, 2014 at 01:47 AM. Reason: title wrong

Jan 15, 2014 | 05:17 PM

Franklin2

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Here is a link with some things to check. I would just make sure the test connector was not corroded.

Fuel Injection Technical Library » No Codes?

Jan 21, 2014 | 12:38 PM

E-5-USMC

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got codes

ok thanks to you i found a bad ground to computer now i have codes 21,23,24,31 now codes 21,23and 24 have been fixed just now code 31 im not to sure whats going on there any comments or thoughs would be helpful

Jan 21, 2014 | 03:42 PM

Franklin2

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Code 31 is something wrong with the EGR. I believe the trucks had the system with the position sensor on top of the EGR. The guy in the book says if you get a code 31 during the engine off code test, the computer is not liking the voltage signal it's getting from this sensor(too low, less than .2v). The orange wire is the 5v power wire to the sensor, the black is the ground wire, and the signal wire(0-5v) is the other wire.

This is the way it works; If you follow the vacuum line from the EGR valve, you will run into a vacuum solenoid valve. This solenoid valve is controlled by the computer, and when the computer tells the solenoid to open, vacuum is applied to the EGR valve and it starts to move. When it moves, the sensor on top of the EGR valve starts sending a different voltage back to the computer, and then the computer knows the EGR is actually opening when it told the solenoid to give it vacuum, and the sensor also tells the computer how far it opened. The computer then turns the solenoid on and off, giving the EGR more or less vacuum to keep the EGR open a certain amount for what the computer is programmed for.

Jan 21, 2014 | 03:44 PM

Franklin2

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P.S. I am glad you found that bad ground. Problems like that are hard to find.

Jan 21, 2014 | 08:22 PM

E-5-USMC

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thanks man you have been a life saver so far lol but got one more question ! did key on engine on test got a code 25 = Knock not sensed during dynamic test now i see that this sensor is not made anymore im going to check to see if its unhooked but other wise what should i do can i bypass ? also i read that computer will keep changein the timeing till there is a no start is this true? and how bad will it affect my fuel eco?

Jan 21, 2014 | 09:03 PM

Franklin2

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When you do the engine running test, whatever you are using will signal you to goose the throttle after it gives you the codes. Did you do this? If it still gives you the knock code, the guy in the book says run the test again, and when the computer signals you to do the goose test, take a hammer and tap on the exhaust manifold and see if the knock sensor code goes away.

The knock sensor is just one of those "icing on the cake" sensors. If it sends a signal that it hears a knock, the computer will retard the timing a little bit, but that's all. It won't affect it too much.