Hey guys, just finished refreshing my emissions system because I didn't pass smog, I replaced my EGR valve but am now getting a fault code 31 for faulty EGR Valve Control Sensor. I didn't get this code before, I got code 33 for a stuck EGR valve. My vacuum hoses are all good my connections are all good, is that sensor really bad and it just didn't understand with the old EGR valve or did I hook something up wrong or what? How would I test the sensor?

Thanks for the help

 

When is this code displayed? KOEO, Stored Codes, KOER?

The definition changes slightly for KOEO/KOER vs Stored Codes.

KOEO/KOER: EVP circuit below minimum voltage of 0.24 volts.

Stored Code: EVP circuit has intermittently failed below minimum voltage of 0.24 volts.

Here is some information about the EVP sensor and how to test it: EGR Valve Position sensor (EVP)

 

The code is displayed in all 3 tests

 

@rla2005 what I was really wondering is are there any other reasons it could show this code besides that the sensor is just bad?

 

One of the causes listed in my Ford manual states a collapsed EGR valve diaphragm can cause that code. An open or disconnected EVP sensor could trigger that code since there would be zero output. These earlier trucks do not appear to monitor the EVP output to see if it changes when the computer commands the EGR open. That's why you can use those cheapo EGR simulators without triggering a CEL. The later trucks that is not the case, so you would get an EGR opening not detected code.

Best advice is to measure the EVP output KOEO using a DVM. It should be between 0.24 to 0.67 VDC. If the signal is in that range and Code 31 appears in the KOEO and KOER tests then you need to verify that signal is getting to the computer. If it is getting there then you are looking at a bad computer possibly. This is not a common failure mode.

If the EVP output is low then you are looking at a poorly made replacement EGR valve or the EVP was marginal to begin with and now with a new EGR valve the tolerances are stacked against you. Be aware if you do replace the EVP sensor many of them have a too long actuator shaft. When you install it the output may be too high now. If that is the case there are two options. Use a thicker o-ring when mounting it or lightly file the shaft down to bring the output back into range.

 

Thank you, that is helpful information, I understand how the sensor works a bit better now. The tolerances seem very small we'll see how long it takes me to get them right.

 

New sensor fixed it so new valve and new sensor must have had the correct calibration together