Error code PO401

[SnookMan]

I just bought a used '02XLT V8 and on the drive home, the service engine soon light came on. I hooked up a code reader, and the error code that came up is PO401. I see that it refers to the DPFE, or differential pressure something or other sensor.
At the same time, I'm getting an incredible humming in the rear end that I'm suspecting to be the diff bearings that I've read about in various threads on the forum.
My question is this, if my differential bearings are bad, would this trip the DPFE error code? In my reading I see that the sensor actually has more to do with the emissions system, vaccum lines and EGR, etc........more than the diff. Am I correct in this? Also, how hard is the replacement of the sensor and where is it located. I know I know, haven't bought the manual for this truck yet........
Any advice would be greatly appreciated

 

[NEWFS02X]

DPFE sensor

Hello. Replacing the dpfe sensor is a piece of cake. It's located on the passenger side of the vehicle. Has a harness plugged into it and has two hoses coming from it. It attaches to two stainless tubes that run vertically downward to a larger pipe that runs from the exhaust manifold up to the egr.

Merely disconnect the harness. Slip the dpfe sensor out of the two rubber hoses and insert the new one. Mine came with new hoses so I slipped the hoses up from the tubes and left them connected to the old dpfe sensor.

Clear the codes and you should be fine.

The rear end hum could be bearing related or on some of the 02's the gear pattern was set up incorrectly from the factory. Mine has a rear end hum while on the throttle...gone upon deceleration.

Usually you can swerve (be careful) from side to side on a clear stretch of road and see if the hum changes intensity or disappears. That usually indicated a bearing problem as by doing this you are loading and unloading the bearing.

It is in no way connected to your sensor problem.

Hope this helps.......John

 

[SnookMan]

Hey thanks John for the quick and VERY informative reply!!!! Yeah it was somewhat confusing having the dpfe code, which by the name alone one would assume that it pertained to the differential, and also having the rear end hum.
But I'm headed out now to swerve around the neighborhood a bit........neighbors already think I'm nuts, this will just be the icing on the cake. LOL
Thanks again.........Lex