check engine light on 1993 Ford F-150 Lightning

my check engine light on my 1993 lightning has been on for over 3 years now.i had it checked out with my garage,an he told me the code it through was for the EGR valve.so i replaced the part myself,including the sensor that bolts on to it.an it is still lit.it idles fine a runs perfect.but the check engine light being on is killing me.what else could it be if the problem says egr.any answers to this question will be greatly appreciated.

1 answer 1 comment
If you have replaced the valve as I outlined in your other question I need to know how long it takes for the light to come back on. You could have a vacuum problem that is not opening the EGR valve when it is commanded open. Your vehicle should be OBD I certified, to check this look at the sticker under the hood with the emissions information on it. There is a part at the bottom of the sticker that says vehicle certified for sale in California or 49 states etc. then in that same paragraph it should say OBD I or OBD II. Disconnecting the battery as mentioned before should clear the codes, on OBD II you may need to use a scan tool to clear the codes. If the light comes on immediately after start up then there is probably a wiring fault and that will need to be traced to the source. If the light takes a while to come back on you may have a vacuum concern or the rare engine control module fault(very rare for this vehicle). Vacuum concerns range from a bad or missing reservoir, broken or cut lines, erratic vacuum solenoid or plugged solenoid vent filter.Good luck.
the engine light turns on about 10 or 15 seconds after i start to drive away.