Hi, I hope I am in the right place. I am a newbie here (Hi everyone) Anyways, I went and had emissions done today it came back with code P0401 of course EGR flow insufficient D. The weird thing though is that my check engine light was not on! It had been on in the past and we had to change the battery terminals (that was 3 or 4 months ago) so it never came back on. Also, when my dad had the truck he had already replaced the EGR valve (about 1 year ago). So guys any other ideas as to what it may be? All your help will be much appreciated! Thanks.
Jodi

 

Not sure if this is the case, but some codes clear them selves, others just turn the light off but remain in the memory and require a manual clearing. If that's the case, some auto parts stores will check and clear codes for free.

 

That code is probably the most common one discussed around here.

Plug it into the SEARCH tool for hundreds of posts.

 

Thank you Salty69! Project I have read about the code EGR valve, Dpser(sp?) and so on. What is making me weary is that the fact the light after changing the battery terminals is not coming on anymore. Even when you turn the key but not crank the engine it still won't illuminate. I have checked the fuses and wiggled some wires, lol.

 

If the CEL doesn't come on when you turn the key on, the bulb is probably burned out. If so, that should have caused you to automatically fail the emissions test.

 

*UPDATE* Project yeah you are right. I pulled out the column last night and replaced the bulb, it was blown. Then I replaced the EGR valve, light still came on. Then I replaced the DFEP sensor, the light is still on. I am at a loss right now. When I cleaned out the EGR valve I clean out the part that bolts the EGR on it, the long pipe though I could barely clean. I was thinking about taking a toilet augar thingy and try and clean out the long pipe that goes to the exhaust (?). If you all have any more ideas let me know. Thanks

 

pull of the dfep tubs tha go to the exust take a a pip cleaner and some carb cleaner and clean the build up out of the little tubs should help

 

Hi,if you take the upper intake{the pipe between the throttle body and lower intake} off and look at the egr passages..Chances are they are clogged..i use brake clean and a pick and bottle brush to clean the carbon out...The problem is the egr flow takes a 90 degree turn into the intake,it gets clogged..About an hour job..Dont try to clean it still mounted on engine,you will cause yourself more problems..You usually can reuse all gaskets but sometimes the throttle body to plenum gasket tears..So good idea to purchase a throttle body gasket before hand..good luck