chaserthedog

I am getting a code P0401 on my code reader. I tested the solenoid for 20ohms (and got 30ohms). I eventually replaced the EGR Valve and EGR Vaccum Solenoid. I am still getting code P0401. I am going through the diagnostics in my Haynes Repair Manual, and I cannot find the BACKPRESSURE SENSOR. Where is this thing? Once I find it I can test it.

fndwl

Hello,
I have a 98 Mercury Sable with 24v DOHC and had trouble finding The DPFE sensor. (this has to do with the code 401) anyway check on the driverside of the engine mounted on the side of it. It is hard to see as it is under hoses,wires there is one plug in it and two vacuum lines comming off the bottom of it.

taurus guy

Just follow the vaccum hoses from the egr valve. 2 hoses should go directly to the sensor. No need to diagnose the sensor, just replace it. It is almost definitely bad as this is a very common problem. One other thing you could check is a crack in one of the 2 vaccum hoses but the sensor, otherwise known as the DPFE sensor, is most likely the problem.

fndwl

I replaced my dpfe sensor yesterday and today the 401 code came in again.
The hoses are fine. Any other suggestions?

taurus guy

Did you clear the code with a scanner (or disconnecting the battery for a little while) after replacing the sensor? If not, try that.