Ive got a 89 f250 that i am having trouble with. It is due for emissions soon but i cant seem to get rid of the check engine light. It is giving me a code 31 which is PFE(Pressure Feedback EGR sensor) or EVP(EGR Valve Position sensor) circuit below minimum voltage of 0.24 volts. I have 20+ in Hg coming in to the EGR control solenoid but nothing going into the EGR. I replaced the EGR control solenoid but light still came on. I checked the voltage with the engine running at the EGR control solenoid and i got 12+ volts. I checked that i have continuity between the connector for the EGR control solenoid and the ECU, good there.I know that the EVP works because when i apply just 2-4 in Hg to the EGR itself the check engine light goes off. At this point i am at a loss and do not know what to do next. Any advice would be much appreciated. thanks.

 

Did you measure the EVP output signal? DTC 31 indicates the signal is below .24 VDC when the EGR is closed. The most common causes of this code is a bad EVP sensor or a collapsed diaphragm/spring in the EGR valve. It is very tough to split the two apart when troubleshooting. Best advice is to replace the EP first, then the EGR valve.

I suggest to check the output signal to verify the circuit is not open. Measure the signal KOEO, then apply some vacuum to the EGR to see if the output signal increases in a linear fashion.A meter check will eliminate unnecessarily replacing parts because of a wiring issue.

 

Went to the junkyard and bought a EGR with the EVP($9) that looked like it was a little cleaner than the one that was on the truck. Put my vacuum pump on it to actuate it and the needle was a little stuck so i lubed it up with a little 3 in 1 oil. Slapped it on, reset the continuous memory(which i forgot to do after i replaced the EVP) started up the truck and no check engine light. i just read elsewhere on the forum that the computer keeps trouble codes for 30 engine starts. might have saved me some trouble. good learning experience.