Ve got a 1988 f150 lariat 5.0. I got a code 31 today. It says PFE,EVP,or EVR circuit below minimum voltage. Any help? I know what the EVP is. It has 5 reference volts like the book says. But that's all I know. What is PFE and EVR, and what could be my solution. Engine runs real rough

 

I had a 31 that I fought through for awhile. In the end it turned out to be the egr valve. Unfortunately I replaced the sensor first, that's wasnt it. The I tried cleaning the valve real good, no help there either.

 

That's what I've been thinking. Just wasn't hoping since I'm broke right now. Maybe I'll hit the junk yard Monday.

 

I just fixed my code 31. I swapped out the EGR and EVP for an extra I had and it fixed it. I know my EGR was bad by testing it so it could have been just that.