po401, po402, po446 codes 96 5.0 liter

[ksperez]

Please Help!!
I have an 96 explorer with a 5.0 liter that has had these codes for several years. Truck runs fine. Ran truck for 100,000 additional miles with no trouble. Went to go to emmisions and the truck won't pass beacause the codes. Cleared codes drove for about 1 mile and the the CEL came back on. Does anyone know where I should start due to getting code 401 gas recc. flow insuff. and code 402 gas recc flow excess? I'm sure that must mean something getting excessive and an insufficient gas flow? And how about PO446 (evaporative Emiss control sys vent control circuit malfuntion)? Any suggestions?

 

[V8BoatBuilder]

Try replacing your EGR DPFE sensor, located on the intake manifold, near the firewall. A bad DPFE sensor will cause these codes. A broken EGR valve would also, but to get both insufficient and excessive flow codes leads me to believe it is the sensor.

As for the EVAP code, check your gas cap.

Welcome to our site. These issues have been discussed many times, so please use the search function and I bet you'll find what you're looking for.

-Aaron

 

[ksperez]

Went to search for the EGR DPFE sensor and i can't find it. So I went to the dealer and picked one up. Upon returning home with the new part in hand I determined this part does not go with my 5.0 V8. The sensor given to me is for a 4.0 V6 by all the pictures I could find. Anyways I removed the egr cleaned it (very dirty and was stiff until i cycled it numerous time) and also removed the device that was attached to the short little hose above it (does not look serviceable). Put all back together and I am getting po402 codes (3times) . A little progress I am not getting po401 anymore. Anyone out there who can help. Trying to avoid changing both parts just for fun!!!

 

[ksperez]

Update Numerous PO446 codes

Well I ended up changing my egr valve. This worked and I no longer get po401 and po402 codes any longer.

However I am getting several po446 codes upon running the vehicle for a short time (15 minutes). The CEL does not come on at highway speeds but as soon as I slow to an idle or if I idle the truck for a half hour or so it will come on. Reset many times and thats what I have noticed. I've tried greasing (lubing) the o-ring on the gas cap as indicated in one thread. (NO LUCK!!). If you draw a vaccum on the cap it does open (release) without much draw. The valve does not seem stuck.

Any suggestions where to try next? All help appreciated...

 

[performancenut]

Possibly a VMV=vapor management valve. Front driver's side frame rail. Fixed my gas cap light with this.

Closely inspect vacuum lines; I ended up with a marked vacuum leak at the heater control valve; to make a long story short the vacuum release was great enough to set off several codes not directly related to the issue at hand.

Do the DPFE; inexpensive and will eventually go bad anyway if not already.

 

[RammaR]

I just got the P0402 code yesterday on my '96 4.0. According to my Haynes manual all Explorers up to '95 and the '96's with 5.0 use the PFE sensor instead of the DPFE. '96 4.0's and all 5.0's starting in '97 use the DPFE. This might explain why the sensor you got doesn't fit.

Good luck.

 

[Nitrous SSC]

Do exactly what V8BoatBuilder recomended. Change the DPFE sensor. Its located on the back of your intake manifold where the throttle body meets. Its a ***** to change but it fixed the same codes you are throwing.

Just go to your local parts store and tell them you need an EGR presure sensor.

 

[RammaR]

I think he has the PFE sensor on his '96 5.0 and not the DPFE -- but that's likely to be the cause.

 

[ksperez]

Update:
I changed the gas cap and the pfe sensor and I am still getting a po446 code. I went to another forum and was told to drop the charcol cannisters and the vent solinoid located above the spare tire. The bracket is held up by three bolts and the area was very rusty. I was able to drop without much trouble. What I observed was a vent soliniod which opens and closes during normal operation. I don't know if this device allows air in or out but I can tell you I popped the top of the vent off and the screen was completely clogged with dirt and road scum. The solinoid remains in the open position until power is applied and the rubber diaphram moves foward and close. This worked flawlessly. After cleaning the (vent) filter and reinstalling I haven't recieved a po446 code in several hours of operation. Usually got a code in 10 minutes or less. I think I've fixed it. And if you read all the possible causes of a po446 code this device is listed and is part of the emmision cicuit control system.

Thanks to all who helped!!!!

 

[V8BoatBuilder]

Interesting fix. I had no idea - thanks for figuring it out!

 

[ksperez]

Still no CEL

Just an update. 10 days of running and no codes. Finally!!!!!

 

[SKYWLKR]

I can verify that the po446 code was cleared permanently by cleaning the filter above the tire. Three days strong (NORMALLY POPPED WITH IN 5-7 MILES) and got it inspected today!!!