97 lx450 CEL code P0401, what should i do??

[myLX450d0e]

Hi i have a 97 lx450 with 260k miles. It has code P0401. I replaced my EGR valve. Nothing happened. What should i do? Should i replace my solenoid, it seems to work just fine, i think.. when i open the blue cap, it is wet and the spongy thing is kinda brownish. Im thinking my switch is malfunctioning. I read alot here and there, but i want to know your guyses advice and input.
I did a seafoam, and carb cleaned my intake mani somewhat. I will be taking it out this weekend and inspect/clean as well as my egr vsv (vacuum switch valve) under the intake mani.
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[94SRUNNER]

Search is your friend. Additionally research the FAQ section, it has loads of great of info.

 

[Pin_Head]

It is usually a clogged intake passage. Remove the upper intake and ream it out and reassemble it and it will be good for another 20K before you need to do it again. The junk is due to poor oil control on high mileage engines.

The other option would be to install a resistor across the temp sensor which will make the check engine light go away without fixing the EGR.

 

[Rookie2]

My p0401 was solved by replacing the VSV. I think that is the most common culprit.

 

[Parsnip]

Mine was the modulator. Read this thread https://forum.ih8mud.com/80-series-tech/363575-p0401-defeated-pics.html

I stuck a pic of my modulator on the last page. Easy check to pop the top off the modulator.

 

[lxcruiser]

Easiest access is to remove the egr temp sensor and have a look inside. Then Ohm out the egr temp sensor. Should be around 750k
ohms or less. Mine was wide open. Good luck

Dave

 

[myLX450d0e]

Where is the egr temp sensor? Is it under the intake manifold?

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[Pin_Head]

It is on the intake manifold opposite from the EGR valve. You need to download a copy of the FSM. It shows where everything is and has an excellent troubleshooting guide for the EGR and its associated DTCs. Search.

 

[CruiseOrlando]

It's not that simple with an OBD-II truck.

I did the resistor thing for my truck (you don't even need to do that - just short it out and it works), it's a 94. The OBD-II (1995+) trucks require more work.

Read this thread for a lot more info - probably the best on this forum so far as the EGR/VSV delete stuff goes:

https://forum.ih8mud.com/80-series-tech/611280-removing-egr-pair-vsvs.html

Also linked in that thread is this post, regarding the OBD-II stuff:

https://forum.ih8mud.com/80-series-tech/437888-egr-readiness-achieved-egr-removed.html

 

[Parsnip]

BTW I found a set of bottle brushes for cheap at HF. One of them was absolutely perfect for stuffing into the EGR temp probe's hole and with intake cleaner spray I was able to clean through the intake into the bottom of the EGR valve itself.

As for measuring the resistance of the EGR temp sensor you may find that unless you bring out your good Ohm meter that it reads open. If it does then give it a few seconds of a cigarette lighter waved under it to heat it without heating it too much. As it warms the resistance should drop and be readable even with the el cheapo meters.

I used 0000 steel wool and intake cleaner to make mine shine like a new penny while I had it off.

 

[jcardona1]

When I first dealt with P0401 my problem was a bunch of cracked vacuum hoses. I also cleaned the intake ports for good measure. Several months later the code came back again. This time the VSV tested out to be fried. So far so good after a few thousand miles.

Point is, you can't just come on here and ask "how do I fix P0401" because there is no one step to fix it. You need to test and diagnose several things before you start blindly throwing money at parts.

As mentioned, get the FSM and follow the steps for dealing with this code.

 

[myLX450d0e]

@jcardona1 well thanks for your advice and your side of the experience. I asked because i tried looking around so much, i have an obd2 sensor and diagnose it, i dont want to throw $$ at parts anymore like i did with my egr valve. Hoses are fine, so i think its probably just the vsv. what my real question was, what was everyone experience if they had this code, and what did they do to fix it and maybe i could imitate that as well and get some more insight on the code P0401. I believe that the egr system is a complex component of the automobile to fix because there are so many parts to it. I hope i lose my check engine light soon thanks too all the good advice.

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[jcardona1]

If you need a VSV, give this one a try. It's what I'm using on mine since I didn't want to pay the ridiculous OEM prices for a stupid vacuum valve.

http://www.amazon.com/Dorman-911-85...qid=1391063544&sr=8-1&keywords=dorman+911-850