P0401 Defeated - with pics (1 Viewer)

[Flank]

I started to throw a dreaded P0401 code that was constant, and recurring immediately after clearing.

I have the FSM, and read God knows how many EGR and P0401 threads - More than enough burn my eyeballs and confuse the hell out of me, so I decided to dive in.

Preparation -
I had decided to take the upper intake off - the better to see what I was doing and learn what is under there - as well as replace the vacuum hoses under there. I also decided to pre-order the apparently most common failure parts - The VSV for EGR and the Vacuum Modulator (right off of the EGR valve, had previously tried to clean - it looked rough).

First: I will list the parts I ordered and or used:
-Throttle Body Gasket 22271-66010
-Upper to lower intake gaskets (2) 17179-66010, 17171-66010
-VSV for EGR - 90910-12079
-VacuumModulator for EGR - 25870-66011
-EGR Valve Gasket - 25627-66010
-Water Hose Clips for hoses into TB - 96135-51300
-5/32 ID Vacuum hose - 'bout 9 feet total
-1/4" ID Gas line hose (for gas and water lines replacing)
-5/16 ID vacuum hose - Bout 2 feet-ish
-Fuel Filter - 23300-69045 - It was right there - might as well...
(edit to Add cleaners)
-new bottle of Simple Green for general cleaning and de-greasing without harshness
-two cans of Throttle body cleaner
-Spray bottle of water to wash Simple Green off of engine
-Cleaning brushes - Tooth brush, nylon brushes, etc for cleaning
-Lots of the Blue paper shop towels.
(I was doing this in my garage, did not want too harsh of chemicals hitting the floor)
-I cleaned parts requiring Throttle Body Cleaner on an oil drain pan - the kind that has a hole in the top keep the oil until you can dump it - so solvents drained into it and did not have risk of spilling in garage.

I had a very dirty engine to start with, thanks to recent rain and big Vegas desert mud puddles. I took pictures of all assemblies prior to removal, in case i had trouble remembering how it went together again.

-I removed the Air cleaner and MAF sensor, intake hose, and per the FSM, removed the throttle body. It was very dirty, doubt it has been cleaned in the engine's 15 years.

-Removed the EGR Valve.

Here is what the intake and throttle body looked like:

 

[Flank]

Intake Removal

Next was the upper intake Plenum removal. This was hard to figure out, as the FSM says what to do, but not how to do it.
There are 6 bolts and 2 nuts to take it off, not including several hoses attached to either the plenum itself or components attached to it. the front 5 bolts can be removed from topside with a small ratchet (all 12mm), the final three require getting at from under the truck with three 12 inch extensions on your ratchet.

Seriously, just surrender the the fact that you will be on your back, under the car. Goes much easier mentally if you do. The intake bolts are EASY to remove when you do it from underneath, and you will need to put them back and torque from under as well.

Here is what it looked like after removal:

 

[d0ubledown]

awesome! just what ive been hoping someone would post up P/N's and all. FAQ material. did you drain the coolant as per FSM? not sure why that has to be done..? did you reroute the VSV? perhaps i'll finally do my vsv this year...

 

[Flank]

Upper Intake off.

With the intake plenum off, I found that my port from EGR valve to throttle body was VERY plugged with carbon, almost totally blocked. Had to chisel it out before cleaning it up. (pic below)

Flip intake over and see the VSV. (See Pic)

There are actually two VSVs under the Plenum - one for EGR and one for the fuel system - they look almost identical. The dealership ordered me the wrong one, and I had to wait an extra 2 days to get the correct one after figuring it out.

I removed, sized, and replaced all vacuum and gas hoses in the top end of the system that I could get to.

(edit to add) I also removed the EGR temp senor that sits opposite the mounting position of the EGR Valve and cleaned all of the carbon build up off of it.

 

[Flank]

Getting questions as I write:

I did not drain the coolant - there are two water hoses that attach to the throttle body - i spilled maybe a cups worth of coolant. - I had just recently done a flush with Toyota Red, and was not about to waste it!!! If I did it again, i still would not drain the coolant.

I did not re-route the VSV. i figure it lasted 15 years in the stock location, it would probably be just fine in stock location if I replaced it all of the hoses associated with it.

 

[Flank]

Cleaning and other

Next I took to cleaning everything - Throttle body, intake, engine compartment and components, including valve cover, distributor, pulled plugs and checked, etc. The engine was filthy, wanted it to go back together cleaner.

Replaced all vacuum hoses to the EGR modulator from the TB, all the little hoses on top of the engine. Most are small 5/32 hoses, but the little guys added up - thus the 9 feet of hose.

After all was clean - took a big breath and went to bed.

 

[Flank]

Putting it all Together

I decided while the intake was off, I would do the fuel filter. My advice - do it then, and for the love of god, remove the fuel lines BEFORE unbolting the filter... Don't ask, just trust me... what should have been a 20 min job ended up taking about 2 hours, of which I don't really want to get into, but it involved a lot of swearing and eventually a clamp to hold the filter in place to remove.

The next night, I started putting it all back together. As I had surrendered to laying on my back under the truck, the intake went on (with the new gaskets) very quickly and easily, and re-torqued quickly.

From there, the project just flew together - very easy to reattach everything I had spent a few nights cleaning.

MOMENT OF TRUTH
I started the car - waited for the fuel to hit and the truck started - and bucked like a friggin Bronco!!! freaking out, I turned it off. Restarted and it did it again! Shaking from side to side violently. I jumped out and listened to a hideous roaring sound - and spied the open port for the EGR temp sensor .... Plugged it with my finger and the engine settled down and hummed.

Got the temp sensor back in, and it ran well, but not as well as I would have hoped - it was idling at about 1000 to 1100 rpms...
It was 1am, so I shut it down and crawled into bed.

Next day, I drove it and no code!!!!!!! The idle settle down to the proper 600-ish RPMs. I guess the computer had to learn the new cleared configuration, because the more I drove it, the better it ran.

Now three days later, code is gone, it is running smoother than before, and a pinging I had is now gone.

WHOOO HOOOOO

So, in conclusion - could have been the blocked port, could have been the VSV, could have been the EGR modulator - did em all, and appear to be GOLDEN. As this was my first time getting into the engine for anything more than plugs, I was very happy with the outcome. My thinks I'm like a friggin' mechanic or somethin'!

 

[Flank]

Forgot to add:

Pic of cleaned port that was blocked, compare with earlier blocked port pic.

 

[gisham]

great write up!

 

[bpassmore]

how many miles do you have?

 

[PHIL O]

great write up. tell us about the performance difference

 

[grizzlygibbs]

Very FAQ worthy I believe, good job, I feel more confident in tackling the vsv now and you just convinced me to get r done!

 

[Flank]

Mileage

I just turned over 206K miles. On performance - I am noticing much smoother driving, and less pinging. I can't logically account for this, but still. My commented on it too when she drove it. I will have to wait until next tank to update any mileage changes, I was getting about 12-12.5 city on average.

Another note: I did not pull the fuel injectors, as I did not have the time to do so and have them sent off to get cleaned, but they are right there - starring at me and mocking me. "pull me, Pull me..." I think it would be an easy job, even for an engine noob like me.

 

[rhyary]

This is excellent.
Very important read if the HG is going to be done.
When I had the HG, I got all the parts Flank mentioned as well. It make the HG job a bit more expensive, but diffidently it is the right time to do all this as well.

 

[jlg32281]

Did you find that it was necessary to use all new gaskets or did the originals appear to be in good enough shape to re-use them?

 

[Flank]

All of these gaskets are metal - the kind that are paper thin with a raised gasket area - and they crush when torqued to spec. As such, when you remove them the raised area that does the sealing is now ineffective, in my opinion, for a re-seal.

When torquing into the Aluminum intake plenum, you are only using like 15-16 ft/lbs of torque - barely past hand tight - so thousands of an inch are very important . I would expect leaks if you reused the old gaskets.

To check for vacuum and gasket leaks, I started the engine cold and sprayed intake cleaner around all areas. From what I understand, if there is a leak, the spray will be sucked in and cause a change in idle.

 

[edog's 80]

Nice work, exactly how I did mine. If it helps at all, I sweared a lot too when I did my fuel filter..

 

[Diesel Wannabe]

I just got the P0401 Code. What was the cost for your parts list? Was this a CruiserDan order/price or was it through your local Toyota dealer?

Thanks.

 

[jlg32281]

I just got the P0401 Code. What was the cost for your parts list? Was this a CruiserDan order/price or was it through your local Toyota dealer?

Thanks.

Good question. Price is important.

 

[wakesetter]

very interesting, especially as I have been ignoring my light for 3 years. Wonder if just cleaning that port would done it. Might try that cause I am cheap.