Ok guys i have searched past posts and i have come to a conclusion here. Correct me if Im wrong this is why i am posting this. Po401-the first step is to clean all the egr pipes including an elbow on the intake?? Which i am not sure where its at. I guess i should tell ya what im workin on. Its a 97 f150 with a 4.6 2wd. Its got 160k on it. Ok when i get it all cleaned out is when i start testing the egr and dpfe right. If they are fine, i let the customer take it. Right?? Well thanks i just wanna get this right the first time.

One more thing, the gas tank is building pressure i guess and the cap is letting it off. Every 15 seconds or so u hear the gas cap purge the pressure off, I thought for sure i would find an evap code but there was none. I told them the first step is to put a cap on it. Because they are not suppose to let pressure out only let fresh are in.

Thanks for any replies

 

For this code on 4.6L engines specifically from what I have read on postings ( i.e. what people have reported back as the fix )

45% of the time it seems to be clogged EGR ports, mostly higher millage 4.6L engines. I have read that members have done this after cleaning the MAFS ( as the source of the pinging ) did not keep the CEL off. After cleaning what looked to be completly clogged EGR ports, the CEL would stay off. The pinging was still present after the cleaning of the MAFS from what I have read, this is why they took the next step to cleaning the EGR ports with a pipe cleaner or carefully with a small screw driver.

45% of the time it seems to be the DPFE or EGR and / or the EVR solenoid. Some actually tested it via the volt meter, others just bought new ones and replaced them, and a few have cleaned the EGR in soapy water. one cleaned the DPFE by turning it over on the bench, filling it with WD-40 and letting it soak, then drain out all the black WD-40.

The balance 10% seems to be corrected via cleaning the MAFS only ( the first step above ) or replacing a cracked line ( to the EGR / EVR solenoid / DPFE ).

That is what I have read on the topic, using the 4.6 only.
I would guess that is the correct route for the 4.6, cleaning the EGR ports when you have higher millage.

As for the gas tank, that is interesting. I don't recall myself reading a post on that type of condition. It seems that if the evap canister was failing, that an evap code would be set. Is it blowing out, or sucking in every time ? I don't know if you waiting by the gas cap, to feel around it to see if it is blowing out pressure, or sucking it in.
If you are having a problem with the solenoid on the canister, you can check it with an ohm meter. If I recall correctly it is 30 ohms when the truck is off ( check that one against the service manual ).

Good luck with the project, post back what you find out, to maybe add another procedure to the list, or change the % of probability of correction for the next memeber.

 

I went through the whole troubleshooting thing on my 98 - 4.2L just a couple of months ago - same code P0401. The first thing is to eliminate 1/2 and keep narrowing what it could be. First of all there is a vacuum hose running from the vacuum selenoid valve to the egr valve. With the engine off take this hose off and connect a piece of spare tubing to egr valve and suck on the other end. you should hear the diaphram valve move. If no - bad valve, proceed to clean valve. If yes start truck let it warm to operating temperature and suck again on the tubing to egr valve the idle should slow if no - clean tubing running from exhaust manifold to egr valve. If yes, egr valve and tubing are in good condition and it could be selenoid valve or dpfe sensor. At this point you may have cut the possibilities in half. There is a procedure in the service manual (not with me and have been posted before) that defines how to check the selenoid and dpfe sensor. Before knowing this I replaced egr valve, dpfe sensor, and finally the egr selenoid and that cleared my P0401 code.

Hope this helps

Silver Bullet