To set the P0401 the IAT2 would need to show little to no increase in temp in relation to EGR valve movement.

Either a stuck valve from carbon marbles or exhaust leak.

Josh

 

No other codes and the truck runs great both in city driving and highway. It does not lack for acceleration and power. I recently had the HPOP and ICP sensor replaced and at that time the P0401 code did not exist. I'm starting to think that when they reassembled it they either did not tighten a hose down properly or a hose has a slight leak in it. Now I did notice when I was inspecting the MAP sensor that the hose had been wrapped in electrical tape (not my doing) on the MAP sensor connection. Hmmmmmm. I'm replaing the MAP sensor and IAT2 tomorrow so I'll check that out tomorrow.

 

They come with tape on the hose for whatever reason.

As for throwing parts at it you're going down a slippery slope.

Josh

 

As far as what? Introducing new problems?

Mike

 

Wasting money on parts you do not need... Check for an exhaust leak

Josh

 

Hi mike, yes I would check for leaks first and make sure everything is seated on right and tightened good before buying stuff.

U can pull out the egr valve and start running the truck but leave it plugged into connector. U should be able to see the vanes move up and down. U might need to have someone romp on the skinny pedal while u pay attention to the egr valve.

Dom

Sent from my iPhone using IB AutoGroup

 

P0401 is a conditional code. So that means that the PCM sees it as something has happened and is a result of that something the PCM is telling you what it can see. That a reading is out of the normal. If it was a circuit issue it would read as a egr valve high or low circuit code and is a hard fault. Seems that we are unable to know if there are leaks without being there looking at the truck. And we don't know what sensor is reading out because we cannot see the readings for his engine over the internet. I'm just throwing Ideas out there as well. Also to answer the other question about why isn't it setting a lean code, lean code do not exist on Diesel engines. A gas motor would run a little funny rich or lean with a messed up maf sensor. Diesels run better with bad maf sensors because they do not have a mixture of 14.7 to 1 like gas engines. The mixture dictates the rpm. So the more the ratio of air to fuel changes the more the RPGs change. This is why diesels don't have throttle bodies that control main engine air flow. It's completely controlled by injector fuel flow. So if a bad maf sensor was on a diesel it would read that voltage as an input to the fuel controls, not like a major input that would effect the way it runs like a gas motor. Dirty maf sensors read a small amount less air flow then clean ones. So a lower voltage. So if the PCM wants to see a amount of air flow at a certain rpm and it's lower, it will read that missing air flow as egr flow if the egr valve is open during that time. Making more sense? Exhaust and intake leaks will effect these readings in the same way. They just won't cause the code to set as quickly as it is unless it is a massive leak. That's why I was steered in this direction.

 

The PCM uses the MAF signal to correlate the opening of the EGR. Cannot have the EGR open too much with very little air flow (i.e. idle versus acceleration versus WOT)

The P0401 is set by the EGR desired does not match the actual and also the IAT2 not picking up a corresponding increase in air temp in relation to valve opening.

Most common causes:

Coked up EGR valve
"Marbles" in the EGR intake runner
Exhaust leak.

Hence that engine had just been done, I would reckon the most likely culprit is an exhaust leak on the EGR up-pipe.

Josh

 

That or a bad map or iat2.

 

Thanks for all the information guys. I just bought my first diesel (6.0) a couple months ago and it has the EGR delete so when getting this code I was like wtf? When cleared it doesn't come back right away so I'm leaning more towards an exhaust leak. Going to watch some diesel tech ron videos to see where the leak may be from 🙂

 

Welcome to FTE, maddag. SYK, you're part of the family now - you can come in the front door! Ya don't gotta drag this dead cat (eek, Sean) of a thread in the back door, lol.

Still, my advice to you would be the same I was going to give the "annoyed" OP: chill, bro, as a 6.0 owner, you're going to see plenty of DTCs. You're still running; you're still good, lol. Otherwise, from the first half-dozen posts I read before realizing how old this thread is, I'll bet every possible explanation for that code is in the thread somewhere. Maybe someone could post the Ford procedures, but they prolly don't apply to a delete.

 

It's a 2005 ford excursion that I bought and I must say the previous owner took pretty good care of it. It's runs top notch, without any smoke coming out of the exhaust so that's a good start lol. Still have to go through a dreaded Canadian weather here, so that will be the true test of it .
Thanks for the nice welcome