P0401 Code (1 Viewer)

[monkeypup]

Sorry if this topic has been beaten to death but I got a check engine light today read the code and it was p0401 insufficient egr flow. I read some other threads about this and checked the egr controller, it was pretty black looking.

I was just wondering what this means and what I need to replace, it sounds like just the contoller/modulator from the other threads. Furthermore, can I continue to drive it before I fix this? I'm a senior in college and it's almost finals week so I can't really be without transportation.
Thanks

 

[napir]

P0401 is an absolute rabbit hole of a code. It could be a number of different things. That said, you can drive on it indefinitely. You may not get top performance (lol) or pass smog if you have that to worry about it, but the truck will run healthy.

There's some really good threads here on going down this rabbit hole, just realize you will be throwing parts at it hoping something fixes it. The only exception is clearing the ports which can be done relatively easily.

Start here PO401 and EGR/air intake manifold with pictures

 

[monkeypup]

Thanks! That thread looks super helpful. So I should be good to drive on it now, but I should probably fix it before I pull a uhaul across Colorado?

 

[Tools R Us]

A 4.7K ohm resister and two .110 spade connectors will solve that! I would be much more concerned about that heater valve.

 

[monkeypup]

A 4.7K ohm resister and two .110 spade connectors will solve that! I would be much more concerned about that heater valve.

What does that mean haha. Please excuse my ignorance. I have very little experience working on my cruiser but I'd like to start fixing some things pretty soon when I start my new job and can afford to.

 

[napir]

It means deleting the EGR from the system, which is fine if you don't have to deal with smog. That said, I've driven across the country a few times with an intermittent P0401.

But as Tools R Us alluded to, definitely make sure your cooling system is up to snuff tho, I'd worry about that before this code.

 

[monkeypup]

It means deleting the EGR from the system, which is fine if you don't have to deal with smog. That said, I've driven across the country a few times with an intermittent P0401.

But as Tools R Us alluded to, definitely make sure your cooling system is up to snuff tho, I'd worry about that before this code.

Does that involve the PHH? I've heard of all this stuff but have no clue what it really is. I'll do some research this weekend. Are there any threads on things that commonly go wrong/should be preemptively replaced? I bought the car at 220k and I'm just about to hit 250k.

 

[Tedward]

Did you remove the top of the modulator?
It's missing. You can see the filter looking thing in the modulator. You shouldn't. The plastic top is MIA.

 

[monkeypup]

Did you remove the top of the modulator?
It's missing. You can see the filter looking thing in the modulator. You shouldn't. The plastic top is MIA.

I pulled it off to look at the filter. I read that it should be white and clean looking in another thread on the topic so I took a look at it.

 

[LC4LIFE]

A 4.7K ohm resister and two .110 spade connectors will solve that!

I am building these, just for your purpose. Install this and plug/block the vacuum lines going to the EGR valve and you will be good to go.

And yes, deal with that heater valve before it's what strands you.

 

[Tools R Us]

It means deleting the EGR from the system, which is fine if you don't have to deal with smog. ...

Don't necessarily have to delete or disable the EGR, that circuit just reports to the ECU that it's working or not. My EGR is functional, but have the resister because it would occasionally/randomly code, has been that way for about 10yrs and just passed emissions, again. It works for our test, others may not be so lucky.

 

[monkeypup]

So a new blue top egr modulator and a new heater valve would be a good place to start? I realize there's a good chance the new modulator won't fix the problem, but the filter definitely makes me think it should be replaced.

 

[WillT]

Could use some P0401 advice. Code only triggers when water temp goes above 182 -184f, and the truck is parked for a short period and then restarted. EGR valve tested good as well as VSV. If you have had these same symptoms and got past the code without deleting it please share.

 

[Tools R Us]

Could use some P0401 advice. Code only triggers when water temp goes above 182 -184f, and the truck is parked for a short period and then restarted. EGR valve tested good as well as VSV. If you have had these same symptoms and got past the code without deleting it please share.

Unplug the EGR thermistor, put a 4.7k ohm resistor on the harness side of the connector, no more code.

 

[WillT]

Unplug the EGR thermistor, put a 4.7k ohm resistor on the harness side of the connector, no more code.

Thank Tools. Are you talking about delete of the EGR circuit?

 

[Loamad FJ80]

Bought this from a fellow mud member...awesome work!!

EGR Temp Sensor Test Plug

I've been check engine free for 300 miles!!

 

[Tools R Us]

Thank Tools. Are you talking about delete of the EGR circuit?

Just the sensor, if you prefer can leave the rest of it functional.