P0401 code, "EGR Insufficient Flow"
Causes
The DPF (differential pressure) sensor is faulty and needs to be replaced There is a blockage in the EGR (most likely carbon buildup)
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
This site might help you out a little more good luck man.

http://www.obd-codes.com/trouble_cod...n-flow-egr.php

 

thanks very much, is this something i shouldn't drive with until it is resolved or can it wait a 4-5 days so i don't have to take time off work to get it in?

 

I am not 100% sure I would say you should be ok doing that.

 

Its not a big deal.

 

I have an '02 F150 w/5.4 and it would ping under loads, 132K miles. I changed plugs again and it helped some. Then I decided to upgrade to 89 octane unleaded and now the pinging it gone. Plugs were always white indicating a very lean condition. Truck still has original O2 sensors but I have replaced the air intake temp sensor. I would like to replace the DPF sensor if you can tell me where its located. Thanks,

 

I just got that same code on my truck with 85,000 miles on it. i removed the egr valve from the manifold but it didn't move more than 1/2" because of the metal pipe its attached to.

i just screwed it back in and said forget it. Where are the ports that need to be cleaned?

 

that pipe is a bit of a booger to get off, the size is a 1-inch and 1/16th. be careful not to round or strip the fitting that holds that pipe into your egr valve.
once you do have it off & replace it, be sure to use an air compressor and blow out any lines going into the egr valve. a good idea that i heard about is putting a little mesh or screen between your egr valve and the gasket for it. this will help filter out carbon and any other junk from getting into or beyond the egr valve; hence if you do get the same code again later you will know that the problem is caused by something before it reaches that gasket and can save some time.

 

You'll need to remove the throttle body elbow and physically clean the EGR ports there. In regards to pinging under load, check your mass air sensor as well.