Originally Posted by USMCWHITENER
Well recently i'v been having problems with my 96 Ranger 2.3L auto with 138K. CEL (Check Engine Light) came on awhile back...P0402 meaning EGR flow excessive. Not P0401 is on. meaning EGR flow insufficient. I have replace EGR valve, Positioning Sensor, O2 Sensors, etc. Anyone got any other items i can check. All help is greatly appreciated.
im not to sure if this setup is like a ford f150, but there is a valve called the dpfe, which controls the vacuum to the egr valve, if that thing got stuck open somehow or is malfunctioning it will cause your problem, to find it just follow the vacuum hose from your egr to it, should have a supply vacuum and a electrical connector to it, and its rectangular in shape and is grey, try replacing that or if you want check for vacuum at egr supply at idle it should be 2 inches or less, if its more, then you know you have found your problem, i hope this helps, looks like you covered all your other bases, this should take care of your problem
btw this is my first post here, just bought me a lil 4 banger ranger