I recently ( 200 miles ago ) did the gotts mod and put a new magna flow exhaust on... performance was good.. mpg went up.. till today! I got the PO402 code ... I read that it is most likely the DPFE sensor... but is it related to the mods? or just a fluke and naturally happened... the truck runs fine.. but, I'll plan on making a trip to purchase a sensor if you guys think that will fix it.

Thanks!

 

You worked right in that area.
Look at the hoses on the DPFE to see if you have one off or faulty.
The EVR may be sticking off normal a small amount causing the EGR to open.
Don't run for parts before you check these things out.
Good luck.

 

the air inlet horn has nothing to do with the problem. Where did you cut and install the new exhaust ? If your way behind the O2 sensors at the CAT, that has nothing to do with the problem either.

 

exhaust I really know wasn't the issue.. but did it the same time.. the original was cut off.. the new was welded in place of... same tail pipe. The truck had an EGR valve issue when bought... and was fixed by either cleaning or replacing the EGR... this was back in December 2011.. could the EGR have anything to do with it? I checked the hoses on DPFE looked ok.. but noticed it was the original metal one. not the new replacement.

 

Here is an example of 'floundering' -around-, the issue.
The 402 code is set when the PCM detects output from the DPFE indicating flow when there should not be any as a check of (system tightness).
A stored value in PCM program when the -igniton is on but motor is not running- is used as the reference value against what is reported by the DPFE.
.
There is flow due to some cause you have to find.
The tube from the driver side manifold , connectig hoses, EGR leaking through to the intake, or the EVR is not fully closed or it's bleed off port has a plugged filter or the DPFE giving a false reading.
You must remember that in addition to the exhaust pressure trying to force flow, that the intake vacuum is also trying pull exhaust gas if anything is open or leaking.
Flow is being pushed from one end and pulled at the other if there is a leak, so one or the other or both is occuring
The DPFE is only a monitor used to report what is happening by sensing the difference in pressure accross a very small orface in the metal tube where it's hoses connect, when it's output is looked at by the PCM..
Otherwise the DPFE does nothing unless commanded by the PCM
This is why I used the term floundering to show you need to look at it from the design opertional point or you need to have some luck in finding the cause.
.
Do the following as an EGR check. Apply vacuum direct to the EGR with the motor running.
If no leak the motor 'should' begin to idle rough or stall as a test -ok..
Go on to the EVR and remove it and it's round cap to clean the filter and the internal moving part with carb cleaner or throttle body cleaner.
Next check out the metal tube for rust/cracking or any kind of leak.
Then if you see no difference, the DPFE is suspect.
More to this than you were awhere of..
Good luck.

 

Thanks... Yesterday afternoon I had to make a 200 mile trip.. So I went ahead replaced dpfe sensor... It was easy enough. 200 miles later no codes yet. I will update if there is a change.

 

That was likely it.
They are subject to carbon, water and any contamination in the exhaust gas.
Good luck.