Did a code scan on my wifes truck today. P0401 Exhaust gas recirculation flow insufficiant detected. P0402 Exhaust gas recirculation flow excessive detected. P0405 Exhaust gas recirculation sensor A circuit low. I need to know which O2 sensor A is. I assume all of these codes has to do with the O2 sensors.

 

Its not the O2 sensor that is a bad EGR valve hence the name "Exhaust gas recirculation sensor " also known as EGR.

 

Usually if you have a P0401 and 402 and 405 the problem is the DPFE sensor and it will need to be replaced.
If you do a search in the forum here you'll find lots of info on that.

 

EGR valves very seldom fail.

Codes at the same time that directly contradict each other are usually due to a faulty sensor, in this case the DPFE as Racerguy suggested.

Since those of us who have been around awhile have learned (like Ford) that their DPFE sensors were crap, just replace it wth the correct Ford (not aftermarket) replacement part.

Steve

 

I had P0402 code, I changed DPFE sensor,it fixed problem.Make sure you get sensor from Ford,aftermarket sensors don't last...