I noticed that right beside the oil filter on my 89 f-150 5.0l on the drivers side toward the front of the truck there is some sort of small casing tied into the motor. It has one electric wire running to the bottom of it and when I screwed it off, it had a small pin hole opening on the thread end and a post for the electrical wire on the bottom. Could this be why the check engine light always flashes.Thanks

 

That's the oil pressure switch for the oil pressure "guage" in the dash. It's really an idiot guage with two positions: either you have pressure or you don't, nothing in between. If the wire is unhooked you will get the check engine light too because it thinks you have no oil pressure.

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1995 F-150 Supercab XLT 155" 4x4 M5OD 302
1986 F-150 4x4 NP435 300

 

So could it possibly be that the wire may have a short in it somewhere, which makes the light flash off and on in the cab. Also I do register oil pressure so would it be a waste of money to replace this unit.

 

If your oil pressure is good, the light is coming from somewhere else. You can pull the codes to figure out if a sensor is causing a problem.

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1995 F-150 Supercab XLT 155" 4x4 M5OD 302
1986 F-150 4x4 NP435 300

 

I'l do that then thanks