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I just bought this 96 Explorer and the previous owner said the check engine light has been on for a year. Reading out the codes, it had set a P0401. I have changed out the DPFE sensor, the EGR valve, the EGR controller, the temp sensor for the computer, and a new thermostat. We have another 96 and I have swapped the new sensors with the sensors off the other Explorer just to make sure I didn't get bad new sensors. All the passages are clear and the hoses and connectors are fine. There is exhaust at both the hoses to the DPFE and the vacuum at the controller is fine. Appling vacuum to the EGR at idle almost produces a stall. The car runs great but will set the P0401 code after about 15 minutes of driving. Some of the question I have are, is there a way to check if the EGR is opening once the temp is up and the car is at cruise, and if it's not, would it set this code, and does the O2 sensor have any input into the EGR controller. I'm about at my wits end, any and all help will be greatly appreciated. Thanks in advance.
I have a 98 Ford Explorer and I also have the same problem as JayDee. I have this infamous PO401 code and have talked with one of the mechanics at the dealership in my town and he did not have anything to say that was helpful. I am also looking for anyone that might have some positive advice. Thanks.
Hey jaydee after looking over your post here we go a lot of factors are involved still 1st are all the replacement parts aftermarket or are they ford oem? There are some wild specs on
these simple looking parts with key on engine off & with a digital
volt meter not an analog one it can feed voltage back into the
circuit on the dpfe relay & dpfe solenoid both check for max ohm's
contact resistance by doing so this ensures full stroke cycle is achieved on both units if both are not up to oem specs this will not allow the obd2 cycle to begin & end correctly which keeps your check engine light on. Worst case senario is that ecm may
need to be replaced or just reflashed but since you have another
one try the other ecm in it's place just to see if it helps. As for the
O2 sensors they all work together but not directly related to each
other it would not hurt to replace them at all on my 98 expy 5.4
i swaped all 4 out & a 7000lbs suv on the highway can get 21.2
mpg no joke now there are other mods i have done but it is not a
4x4. Dude if this is not it WOW!
good luck turbo ted