P0401 Defeated - with pics (2 Viewers)

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Scrootinizer said:
Over the weekend I attempted to tackle my P0401 on my 97 LX450 with 285k, as my inspection/registration is about to expire. I'd replaced the EGR vacuum modulator a couple weeks ago because it didn't pass the test, but that didn't stop P0401 from coming back. I ordered all the gaskets, EGR VSV, some 5/32 and 5/16 vac hose, and dove in.

Removed TB and cleaned, removed upper intake and cleaned out the port (didn't seem to be clogged), replaced EGR VSV and all the little hoses underneath the intake. I left the EGR valve in place because I couldn't get a good grip/leverage on the large nut so I removed the studs and was able to get the upper intake off that way. Put everything back together with new gaskets and hoses where I could.

Started the truck up and was relieved that everything felt and drove the same as before. This was my biggest undertaking on the LX so far and it took me about 8 hours total over Saturday and Sunday. Needless to say, my wife was not happy with me spending that much time on the LX.

Today on my way to lunch P0401 came back :bang:... I don't want to take the truck to the shop, but at this point I doubt I can convince my wife to let me spend any more time fighting P0401.

Any ideas/suggestions before I throw in the towel?
Click to expand...

I am betting you have done all of this but I thought I would offer it up anyway:

How does a mechanic diagnose the P0401 code?
  • Scans codes and documents the freeze frame data in order to verify the problem.

  • Clears the engine and ETC codes and road tests the vehicle to verify whether the codes come back.

  • Visually checks the vacuum hoses, wiring, and connections to the EGR valve and control solenoid along with the EGR temperature sensor.

  • Disconnects and checks the EGR valve is getting enough engine vacuum to the valve when the control solenoid opens on light-to-medium acceleration.

  • Checks for EGR temperature sensor changes and engine to bog down when the EGR is opened.

  • Removes EGR valve and temperature sensor to check for excessive carbon buildup or partial blockage of the EGR tubes from the valve to the intake manifold.
Common mistakes when diagnosing the P0401 code
  • Failing to check and clean the EGR passages when replacing a defective EGR valve.

  • Condemning a good EGR valve when the EGR temperature sensor has excessive carbon buildup on it causing the failure code.

  • Failing to check to see if the EGR control solenoid will hold vacuum before replacing the EGR valve.
How serious is the P0401 code?
  • A failed EGR valve can cause the engine to have excessive ignition pre-ignition that can cause internal engine damage to the piston and valves.

  • The Check Engine Light on will cause the vehicle to fail emission testing from excessive NOx gases.
What repairs can fix the P0401 code?
  • Replacing the leaking or clogged EGR valve

  • Replacing a broken vacuum line to the EGR valve or control solenoid

  • Replacing an EGR temperature sensor or clean the carbon off of it to repair it if it does not register enough of a temperature change

  • Cleaning carbon out of EGR tubes to intake manifold to clear any blockages
 
Thanks for this summary, I hadn't seen this one before. I wasn't able to remove the EGR valve or do the vacuum testing on it per the FSM. Mine looks pretty rusty and according to the PO's very detailed records has not been replaced. I also didn't remove and check the EGR temp sensor for buildup, I couldn't get the leverage with my little 12mm combo wrench so I moved on. I was shocked to see the price of the EGR temp sensor. I may have to take the LX to a shop and let them know what I have and haven't done and hopefully they can narrow it down from there. It's tough to get some time in the garage with a 1.5 year old and not worth making the boss mad... I'm sure y'all know how that it.
 
Are you part of the Lone Star Landcruiser club? If not, you should join. There are guys there that have a great set of tools and would probably come over and help you out. Check it out in the club section of Mud and join. I learned everything about how to set up my stock 80 series for serious off-roading back in 2010 by attending the meetings. LSLC is how I found and joined Mud. Work prevents me from attending very many meetings anymore but I'd prefer to attend if I could make the time.
 
toyonado 451 said:
possible cheaper way to clear this code

Before you try this, move your cruiser outside as it creates a massive amount of smoke. I tried this on my 97 LC with a p0401 code that wouldn't stay cleared after replacing the egr valve and the modulator. (Code came back a few days after i replaced them). I will post later if the code stays clear. basically, I put about 6 ounces of sea foam in a clean glass jar, and after warming up the engine, turned it off, removed the oxygen sensor which is opposite the egr valve (make sure to remove the wiring clip which faces the windshield first, to avoid twisting the wire. use a 14 mm wrench to remove the oxygen sensor). After that I ran a 12 inch black rubber hose, maybe 1/4th inch diameter, from the glass jar with the sea foam to the hole that the sensor came out of. I had a friend start the truck which sucked the sea foam into the intake, (which should lead directly to the carbon buildup.) This causes the engine to stall, but if it doesn't, turn it off as soon as the sea foam is sucked up.
let it sit for about 10 minutes, then, outside with a breeze away from you, start the truck. It will smoke like hell for about 10 minutes, but as the carbon burns off, it gets clear. The truck hasn't thrown the code today, which it would have for sure the day before I tried this. It cost me 6 bucks for the can of sea foam. the only danger i could see would be if the sludge would mess up your valves, or plugs. so although it worked so far, maybe someone who knows more could say if this is a good idea. also, when removing the egr, you can remove the stud bolts using a 7mm star driver which makes it a lot easier to pull the egr.
Click to expand...
 
I want to post that 8 years and 100,000 miles have passed since my original “seafoam code clear” post. I still have the 97 Cruiser, and it hasn’t thrown the code since. The price of Seahoam has doubled though. Good luck. And you have to use the vacuum hose to put the full strength seafoam directly on the carbon plug. Don’t believe the people on here that say that this doesn’t work. It does! The guy that showed me how to do it has belts older than they are.
 
Dealer may be expensive. Depending on where you are located I would look for a independent Toyota shop such as Ryan at OTRAMM www.otramm.com
 
Just keep in mind that even when new the number of Land Cruisers sold by dealerships was small compared to other Toyota models. The experience levels and the number of the Land Cruiser mechanics was minimal back in the '90s. Now over 20 years later the dealerships virtually have no experience with the 80 series. The independents are going to be more experienced and in the long run I would think would be cheaper. Even if you have to travel further it will be worth it in the long run.
 
davesax36 said:
Post in the Blue Ridge Cruisers group. Someone might be able to come help you.
Click to expand...

I think I may have found the problem. It looks like one of my hoses has cracked and needs replaced. here is the hose does anyone have a part number?

image.jpg
 
That is the throttle cable not a hose. Underneath the rubber is a steel jacket. It can eventually cause a sticky throttle pedal. It is not related to po401 code.
 
That is not a hose. That is the throttle cable that runs to the transmission (I believe). Part. Umm as best I can tell is 35520-60110 also can use 35520-60111 based upon parts diagrams online.
 
X2
That is not the throttle cable for the transmission, that is the throttle cable for the gas pedal. Would have nothing to do with P0140 Code.
I had one go bad, led to a sticky throttle cable that kept my revs high. Pulling up the pedal with my toe was the temp fix until I replaced it.
ppc said:
That is the throttle cable not a hose. Underneath the rubber is a steel jacket. It can eventually cause a sticky throttle pedal. It is not related to po401 code.
Click to expand...
 
grizzlygibbs said:
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!
Click to expand...
+2 for a FAQ sticky
 
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