P0401(EGR) New parts + $$. The problem won't go away!

[cadence]

I can't seem to cure the P0401 code in my 1997 Land Cruiser

I have spent a lot of time reading through countless helpful threads on this forum and I have done all the recommended fixes including:
-New EGR valve
-New VSV under the manifold
-Cleaning the port through the intake manifold
-Inspected the main wiring harness next to the EGR pipe
-Inspected for vacuum leaks

What else could it be? Every time I reset the CEL it comes back on anywhere from 10 - 100 miles later

 

[96r50]

Did you check the EGR modulator (the smaller UFO-shaped object)? Sometimes carbon can build up in there too and cause a problem. There should be a thread on inspecting/cleaning it.

 

[95Fantasma80]

Wow I would not want to do all of that and still have the problem....

I agree the EGR modulator should be your next step since you already trough a lot of parts at it...

Or you can buy the FSM and test to see if the EGR modulator is working.

 

[Flank]

Did you just check for leaks, or replace all of the vacuum lines? It is cheap to do, you may have some micro cracks or something.

 

[super90]

Did you clean out both "ports" in the top of the intake, the one circled in red and in blue in post #60 of the following thread?

https://forum.ih8mud.com/80-series-tech/295289-9-times-out-10-po401-code-fixed-3.html#post5010374

The one circled in red is a very common culprit. It was on my truck. No one could find it, so I tore it all apart and discovered the problem.

New vacuum line is indeed good. Vacuum modulators go bad, as do the temp sensors. There are ways to test both.

 

[weigellj]

Step 1: remove all of the EGR crap
Step 2: make some block off plates
Step 3: Install the radio shack resistor. Don't remember 4.7K something (off memory).
Step 4: clear code and enjoy driving with no CEL for EGR Crap.

even if you have emissions, I doubt the tech is going to know it is missing and I "think" it pass's the sniffer as well.

I did it on the wifes 96 about 2000 miles ago with NO issues.

 

[Ebag333]

It'll pass the sniffer. The EGR is not supposed to be active at idle or under load, only at cruising speeds in low load situations. In other words it'd never be active (if working correctly) when you have a sniffer.

The only exception I could think of would be if they put you on a dyno, then you could run into a situation where the EGR would be active. But it should still pass the sniffer.

 

[simann]

Great info!

 

[LandCrawler]

Step 1: remove all of the EGR crap
Step 2: make some block off plates
Step 3: Install the radio shack resistor. Don't remember 4.7K something (off memory).
Step 4: clear code and enjoy driving with no CEL for EGR Crap.

even if you have emissions, I doubt the tech is going to know it is missing and I "think" it pass's the sniffer as well.

I did it on the wifes 96 about 2000 miles ago with NO issues.

Any tech worth a damn knows what a EGR valve is, and if its missing. They also know how to test if its functional. If you remove your EGR chances are you will never pass another smog test again.

 

[Ebag333]

Any tech worth a damn knows what a EGR valve is, and if its missing. They also know how to test if its functional. If you remove your EGR chances are you will never pass another smog test again.

Sure, but what are the chances that they're actually gonna pop the hood and look? Depends on where you live I suppose, but around here it's very very slim.

There are stealth ways of disabling it though.

 

[clownmidget]

At least up to 2007, in California, the inspection stations were stand alone and not in any way affiliated with a garage or able to do any repair work. I suppose to try and reduce a "conflict of interest" where the station doing the inspection could drum up some business by repairing any failure issues.

So I don't honestly believe anyone at an CA inspection station is going to notice any missing or non-functional EGR components. I had a turbo and single cat on a 3-inch exhaust, etc, etc and only once was I close to not passing - for my gas cap.

If I was in CA I'd leave it all in place, plug it all up, leave the temp sender in the intake manifold and put the resistor in the harness side of the connector.

 

[LandCrawler]

Sure, but what are the chances that they're actually gonna pop the hood and look? Depends on where you live I suppose, but around here it's very very slim.

There are stealth ways of disabling it though.

My last smog test (last week) the tech failed me for no vacuum to the EGR. he tested the EGR that it does open (by applying vacuum directly) and listened for the engine to stumble. He also tested by placing a vacuum gauge inline to verify there is no vacuum when there should be.

Even tho the sniffer passed (with flying colors) i still failed visual because of a non-functional EGR valve.

This is in California. The worse of the worse, but other states are following close behind.

 

[LandCrawler]

At least up to 2007, in California, the inspection stations were stand alone and not in any way affiliated with a garage or able to do any repair work. I suppose to try and reduce a "conflict of interest" where the station doing the inspection could drum up some business by repairing any failure issues.

So I don't honestly believe anyone at an CA inspection station is going to notice any missing or non-functional EGR components. I had a turbo and single cat on a 3-inch exhaust, etc, etc and only once was I close to not passing - for my gas cap.

If I was in CA I'd leave it all in place, plug it all up, leave the temp sender in the intake manifold and put the resistor in the harness side of the connector.

Ive had smog shops fail my Turbo charged vehicles because I "added an intercooler". Some shops wouldnt even put my car on the dyno after noticing the aftermarket intercooler and i had to go home and return everything to stock.

CALI SUCKS when it comes to smog.

 

[pkelly72]

If the modulator doesn't work (this is where I would have started 1st due to cost) then try a new charcoal canister (do a search for the GM one). I've been here and it's no fun.

 

[Spadone]

Has anyone heard of this problem (same code) causing your rig to not start when it is hot? Does the FJ80 have a safety feature that prevents it from starting if the vacuum system is blocked - kind of like a vapor lock?

 

[ChiTown]

Spadone- the 80 dies not have such a feature. I would check the fuel pump (actual fuel pressure and that it is cycling), ignitor for the ignition system, efi relay, fusable links. You'll find the issue in one of those.

As for the OP's EGR issue, it's going to be the vacuum modulator or the vacuum tube on the brake booster side of the manifold clogged with carbon due to a blown modulator.

As for removing the EGR components and not having a smog guy notice, no chance any where they do an actual visual check and have half a clue especially in CA, AZ, NV where they have to actually test the EGR system for functionality.

 

[Qball]

My last smog test (last week) the tech failed me for no vacuum to the EGR. he tested the EGR that it does open (by applying vacuum directly) and listened for the engine to stumble. He also tested by placing a vacuum gauge inline to verify there is no vacuum when there should be.

Even tho the sniffer passed (with flying colors) i still failed visual because of a non-functional EGR valve.

This is in California. The worse of the worse, but other states are following close behind.

Wow really? I passed smog a few month ago and the tech didn't do any of that. He did notice I advanced the timing and I had to put it back to 3 to pass.

Maybe your erg caused a CEL?

Unlike many I do however appreciate the strict smog requirements. I lived here 25 years and witnessed dramatic improvement in air quality while number of cars have quadrupled if not more during the same timeframe.

 

[Trux]

Make sure that tiny little hose between the front TPS (throttle position) and the other sensor is hooked up. ( The two sensors on the front of the intake.)

There is a tiny hose below , and right between the TPS and the other sensor.

My code kept going off until I hooked it back up. It's small, and difficult to see without a flashlight. And I couldn't attach it without angled pliers.

It's very easy to overlook after you've hooked everything back up after a throttle cleaning, EGR fixes.

I can take and send a picture if those instructions are hard to follow

 

[Spadone]

Thanks for all of the advice. Another contributor I asked recommended running diagnostics on the ignition system components. I used my Chilton manual and followed the steps to check the igniter, igniter cable and other components of the system. Everything checked out. What I found curious was when I reconnected the igniter cable and started the truck, I got a bit of a backfire. I shut down and restarted and my rig idled higher than normal for a bit then returned to normal idle. I shut down again and everything ran fine. When the truck backfired I got a bit of spray from the exhaust - like carbon.

Could this be a fuel issue. Going for a check ride today. Fingers crossed.