having trouble with my egr vavle again. my 99 f-150 5.4 has had two new vavles and cleaned once. light is back on and showing a 402 code. do i need to trade for a chev?

 

changing the plastic do-dad that is on top of the valve. That's your problem....

 

You need to replace your DPFE sensor. Do not replace your EGR valve. They rarely go bad. Go to the dealer and purchase a new DPFE. They cost about $30. Should take 5 minutes to replace. I had the same code on my 2001 4.6 Expy. Problem solved.

 

Yes, I believe a Chevy is in order here, but seriously. Does it idle ok, not real rough or stalling at idle? If that's ok, chances are the DPFE sensor is bad. Code P0402 means excessive egr flow. If it idles ok, it doesn't have excessive flow. If you have access to a scan tool, monitor PID DPFEGR with key on engine off. It should read .8 - 1.2v. If not replace the DPFE sensor. If reading ok, start the engine and read the pid, it should read the same .8 - 1.2v at idle. If it doesn't, pull the vacuum line off the egr valve. If it reads ok, replace the EVR solenoid. If it reads high, the egr valve is partially open. Keep in mind you only perform this test if the pid reads a higher voltage with the engine running at idle than it does with key on engine off.