I Scanned My 1986 B2 This Weekend And Code #31 Came Up 3 Times "evp Sensor Below Min Voltage" Does This Mean The Evp Sensor Is Just Bad Or Is Something Else Causing This Problem? What Kind Of Symptoms Would I Notice As Far As Performance? I Repaired All The Other Codes That Came Up. Any Help Would Be Greatly Appreciated!!

Dj

 

Try a new gas cap.

 

Was it a KOEO 31 or a CM 31 or both?

 

It Was A Koeo 31

 

Because a KOEO code is set with the engine off, it almost always has to be electrical in nature. Check the wiring between the PFE sensor and the computer, make sure the PFE is receiving the 5V Vref. If the wiring checks out, then check the PFE output. If I remember right, my PFE sensor outputs ~3 V KOEO.

 

I don't mean to offend but rather I just want to check. CM codes are pulled during KOEO, are you sure it wasn't a CM? Also I consulted my book and in a truck 31 can be an EGR valve control sensor fualt (KOEO, KOER, CM) and it can be EVAP control system below min voltage (KOEO, KOER).

 

actually i rescanned it and it comes up as koer code 31 which in my book is a evp sensor below min voltage..i don't know if the sensor is bad or if something else is causing the code to come up..is there a way to test the sensor? and by the way.what is the pfe sensor and where is it located? thanks for all the info!

 

Don't get to caught up in the exact definition of an EGR sensor code from a generic EEC-IV code list. Over the years, Ford used several "flavors" of EGR system. Other systems use an EVP (EGR Valve Position) sensor. The 2.9 L EGR system uses a PFE (Pressure Feedback EGR) sensor. PFE sensor measures exhaust backpressure at the EGR valve. On my '87, it is located on the throttle body next to the EGR valve with a vacuum line going to the EGR valve. Based on the PFE output, the computer uses the EGR vacuum regulator (EVR) solenoid on the fender to control how far the EGR valve is open via a feedback loop.

I can't speak for others, but, in my opinion, testing the sensor begins by getting good information from the EEC-IV self-tests, which still appears to be in doubt. There are two tests that can be performed: KOEO (Key On Engine Off) test and KOER (Key On Engine Running) test. There are two sets of codes output during the KOEO test: KOEO codes are output first, then a separator pulse, then continuous memory (CM) codes.
My advice at this point is to repeat the self-tests yet again (unless you can remember for sure from the last time) and fill in the following table:

KOEO codes (1st set during KOEO test):
CM codes (after separator pulse during KOEO test):
KOER codes:

Don't leave any blank. If you get a pass code (11), note it.