2003Exp 5.4 emission problem

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Mar 14, 2013 | 10:57 PM

ShadowSnowLeopard

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Joined: Jul 2012

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From: Douglasville, GA

2003Exp 5.4 emission problem

Ok, to keep this simple, this problem started three years ago and I have just been working around it. My expedition apparently has a computer power problem somewhere. When they hook up to it for emissions, everything is great till they turn off the ignition, then on restart the computer is cleared like you have unhooked the battery and fails. What I have been doing is just turning the key back to accessory, not off. Kills the engine but doesn't clear the computer. Now, not a big deal I guess since I have inured out the work around, but has anyone else seen this? No error codes and no blown fuses under the dash.

Mar 15, 2013 | 05:23 AM

projectSHO89

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Joined: Jan 2004

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From: St Louis

Check the power feed from fusebox F5 to PCM connector pin 40 (red/white wire). It's supposed to be "always hot" and is used to maintain the PCM's Keep Alive Memory.