I am getting a P0401 & P0411 code on my 1996 F150 with the 4.9L 6cyl. The engine seems to run fine but wont pass emissions. I haven't taken anything apart yet. I'm thinking it might be a clogged EGR valve. Anyone else have this problem? Any suggestions?

 

DPFE or air leak, EGR issue. Look in that area.

How does the truck run?

 

Truck runs perfect. If it weren't for the check engine light, I would never had known there was a problem. Did you ever run into this problem before?

 

P0401 is a code related to the EGR system. P0411 is from the secondary AIR injection system. Two different systems, two different causes. Both are part of the emission system. Either can cause no driveability issues, but they can also trigger a "limp mode" and decrease mileage/performance.

The most common cause of P0401 are the silicone tubes running from the EGR line to the DPFE sensor are aged/cracked.

Potential causes of a P0411 code include:

• Damaged or missing check valve
• AIR pump intake port plugged/damaged
• AIR pump clutch malfunction
• Holes or damage to exhaust components

 

Tomorrow, I will look at these areas. Thanks RLA & khad, I'll post my findings.

 

I checked the EGR valve, it wasn't clogged and I put vacuum to it and it opened. I looked around and noticed a plastic vacuum hose that was broken, it went to some vacuum tank. I reconnected it and now the truck is running like crap. Hmmmm, this emissions stuff is a real headache. I located the DPFE sensor, how do you check to see if it is working?

 

I like this write-up: http://rockledge.home.comcast.net/~r...tage-Test.html

And here is a video: Ford P0401 DPFE EGR Pressure Sensor Diagnostics and Repair with a Contest - YouTube

 

Thanks RLA, I will try it tomorrow and report back. Great site!

 

Yesterday, I looked over all the plastic vacuum hoses. I noticed one hose, attached to a vacuum tank, that was broken. I pulled the broken half out of the rubber connector and re-inserted the other half. I disconnected the battery to clear the codes. I just came back from a 20 mile drive and no codes, check engine light is out. Amazing how much trouble one small hose will cause. I hosed off all the dirt and grime under the hood and must have soaked the distributer. The truck ran like crap because the wires got wet. Once the wires dried, the truck ran perfect again. Thanks to RLA and Khad for all your help. You guys saved me some $$$$$.

 

Glad we could help you out!