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95 F150 5.0L codes 556,558,332

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Old 09-17-2015, 07:30 AM   #1
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Default 95 F150 5.0L codes 556,558,332

1995 F150 5.0L Auto, Codes 556,558,332. Truck runs great but codes won't clear, I've tuned it up spark plugs,cap and rotor, wires,air filter and fuel filter,

Hello all first post and I'm stumped as where to go,I am down to the ecm as the problem. Here is where I'm at;

Checked and replaced evp (new) replaced egr (used) both old and new tested good though.
Checked soup can for holes and it holds a vacuum well,seems OK.
Checked evr and replaced (new)
Ohms on new evr,32 ohms, has 12.8 volts with key on plug removed.
Removed ecm plug checked pin 33 to signal return wire at evr plug, tested good for continuity, ground, and voltage leak.

Vacuum at inlet or evr is 20 in hg at idle
Vacuum at egr,engine warm and revved to 2000 rpm is 0

Checked vacuum lines, then sprayed starting fluid around to check for engine increase and none detected.

Removed double vacuum plug at evr (only upper hose, I left the supply vacuum lower hose attached and attached a seperate vacuum hose from upper port to egr valve.
Same thing 0 vacuum

I think the ecm is not working correctly on the 33 pin circuit but don't know for sure.

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Old 09-17-2015, 07:45 AM   #2
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Also I need to mention I took the evr back to the parts store and replaced it also went to salvage yard and got two used ones and they all do the same thing, nothing. No vacuum at egr valve
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Old 09-20-2015, 10:22 AM   #3
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Just wanted to update in case anyone is reading this and having the same issues.

I found the problem, I have driven about 200 miles and my cel is out and the truck runs better than ever.

I had it narrowed down to the pcm,because all circuit checks were good, components checked good, all vacuum lines checked good. So I thought it was time for a rebuilt pcm.

But after more thought on it, I noticed that the light would go out and fault code would go away temporarily only to return in short order. Through this whole process occasionally the system would function properly at times and then quit all together. Still thinking pcm, then it dawned on me what if the connection or ground wire to the computer was bad.

So I removed the pcm plug and cut off the fuzzy end of a q tip off and dipped it in dielectric grease and shoved the grease in the 33 pin hole, then reinstalled the plug and tightned it down tighter than I really felt comfortable doing. Next went to the ground wire to the drivers fender. Rmoved screw and sanded and cleaned well, also sanded the paint off the fender where the bolt makes contact, then coated the whole thing heavily with dielectric grease.
Doing great so far. hth
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