How do you run the Notorious Check Engine P0401 - EGR System Insufficient flow , out of Town ? ! (1 Viewer)

[FreedomRider]

Just bought a 1997 LC FJZ80 Collectors Edition , 3 previous owners , with 229K , no maintenance history , but no accidents or rust which is a miracle !
Drove it home from PA to South Jersey - approximately 250 plus miles with no issues.
I am a computer engineer and unfortunately not an auto mechanic , but have a close friend who is a professional mechanic. This is the first 80 Series he has worked on.
I took it to him to do a baseline mechanical assessment.
He replaced the following parts:

• Alternator
• AC Compressor
• Sway Bar
• Stabilizer Bar
• Ignition Wires
• Head Gasket
• Battery
• U Joints
• OIL Seal and Changed the OIL and Filter

• BRAKE Rotors
• Brake Pads
• Radiator Hoses
• Spark Plugs

After the parts were replaced he delivered the car that night after driving for approximately 30 Miles / Minutes and turned the car off.
I test drove it with him for another 5 minutes /miles and the Check Engine Light came on with a P0401.

Subsequently he replaced the EGR Valve , O2 Sensors , EGR Vacuum Modulator, EGR Solenoid, EGR Tube and Cleaned EGR Ports , cleared the P0401 and the car sat overnight in his driveway
He delivered it to me the next morning after driving it approximately 30 miles.

The next morning I drove it for approximately 7 miles and the Check Engine Light comes on.
I cleared the P0401 and ran it for 27 miles with no Check Engine light.
Car sat overnight and the next morning while driving to Church , boom ! Check Engine after 7 miles .

What is different / changes from when the car starts up with no check engine light runs for about 30 minutes , cools down and then after 5 minutes /miles the EGR system malfunctions?
The car runs great otherwise! No smoke , noises , stalling , engine purrs , transmission is smooth.

I scheduled an appointment this Friday with a Toyota Certified Technician at my dealership that has a lot of experience with 80 Series .
Will let you know what the root cause and resolution, but curious to see if anyone has had a similar experience and if so what resolved the problem.

Thank you for your time in reading this post. Best Regards, Joe

 

[cahill]

When you clear the code the computer will go through several driving cycles and certain parameters as it goes through it's sytem checks before it will re-flag the code again. My guess is that there is still a port or two that is plugged up in the intake manifold.

 

[Kernal]

Tons of previous discussions on that topic, try a search using P0401. You'll get dozens of hits. Edited, sent pm.

 

[greentruck]

Get a Scangauge or similar. Use it to clear the code and ignore until the Check Engine light comes on again. Repeat as needed.

This may not work if you live in a smog-check jurisdiction, but works for me.

 

[FreedomRider]

When you clear the code the computer will go through several driving cycles and certain parameters as it goes through it's sytem checks before it will re-flag the code again. My guess is that there is still a port or two that is plugged up in the intake manifold.

Thank You Cahill !

 

[FreedomRider]

Get a Scangauge or similar. Use it to clear the code and ignore until the Check Engine light comes on again. Repeat as needed.

This may not work if you live in a smog-check jurisdiction, but works for me.

Thanks greentruck !

 

[FreedomRider]

Was the head gasket replaced ($2000-3000), and why, or was it the valve cover gasket (and spark plug tube seals, PCV grommet) ??

Which oil seal (oil pump cover or front crank seal)? Did he replace just
one of those and not the other??

Why replace the alternator, not charging?

Were the sway bars themselves replaced, or was it the bushings for those bars??


Tons of previous discussions on that topic, try a search using P0401. You'll get dozens of hits.

Hi Kernal
Thank you for replying.
My bad , he replaced the valve cover gasket , spark plug tube seals, PCV valve and PCV grommet .
Not sure which oil seal was replaced (the auto parts list just specifies Oil seal, I will need to ask him)
Replaced the alternator because it looked like it may have been the original
The sway bars themselves were replaced.
Yes lots of discussions on P0401.
I will post the fix once the issue has been resolved. Best Regards, Joe

 

[Kernal]

Here's an old thread that might be interesting:

Disable the EGR system the (mostly) Toyota way

So I recently disabled my EGR system, and was looking into disabling the temp sensor. I was all set to use the resistor trick, when tblume posted his thread that got me thinking. Evidentially, for ODB-1 and ODB-2 trucks there is a very easy way to disable the EGR system. Create an continuous...

forum.ih8mud.com

 

[FreedomRider]

Here's an old thread that might be interesting:

Disable the EGR system the (mostly) Toyota way

So I recently disabled my EGR system, and was looking into disabling the temp sensor. I was all set to use the resistor trick, when tblume posted his thread that got me thinking. Evidentially, for ODB-1 and ODB-2 trucks there is a very easy way to disable the EGR system. Create an continuous...

forum.ih8mud.com

Thanks Kernal!

 

[Kernal]

Here's a link for the EGR Temp sensor test plug:

EGR Temp Sensor Test Plug

Hi Everyone, I figured I would post up a small project I have been pulling together mainly to satisfy my curiosity about EGR bypass, testing, and making it look good. Many of us have experienced the P0401 code and normally it is an EGR related issue. As you will come to find out, especially...

forum.ih8mud.com

 

[FreedomRider]

Here's a link for the EGR Temp sensor test plug:

EGR Temp Sensor Test Plug

Hi Everyone, I figured I would post up a small project I have been pulling together mainly to satisfy my curiosity about EGR bypass, testing, and making it look good. Many of us have experienced the P0401 code and normally it is an EGR related issue. As you will come to find out, especially...

forum.ih8mud.com

Thanks again Kernal !

 

[aclos3]

When you say that your friend cleaned the EGR ports, that might just mean the ports in the direct vicinity of the EGR. What commonly plugs up the EGR system is the channel that runs through the intake manifold. With the throttle body off of the intake manifold (and ideally the intake manifold out of the truck), this port can be seen and cleaned pretty easily. Mine was completely plugged up with carbon at around 220,000 miles.

 

[ajax1]

@FreedomRider soumds like your friend doesn’t know these trucks to well, instead of replacing your alternator he could of just inspected and or changed the brushes for 20 bucks. Hopefully he is using Toyota parts for the seals and engine parts, test the vsv easy to do.

 

[categorytheory]

As others have said... get a scan gauge tool, get a Bluetooth odb2 reader, have the manifold cleaned by a pro. You’ll figure it out. Mine was cleaning the manifold out professionally but you can do it yourself too. And that was after replacing a bunch of parts and all I needed to do was clean the upper manifold....

 

[Kernal]

^^^Ditto^^^, Just did this to my 95 model, the carbon packed in the intake plenum port was like cement, to get things started had to drill it out using a 1/2" drill bit (using the drill) for the section starting from where the Throttle Body attaches to the intake.

The tunnel that's cast into the upper intake and carries the exhaust gas from the EGR valve through the upper intake and dumps it out just inside the TB was a bit more difficult. Took a few cans of Throttle Body cleaner including letting it soak while one end was plugged (so the cleaner wouldn't flow right back out). No good way to get a tool into that tunnel/passageway. Alternated using a strong degreaser then the solvent to break up the carbon. In hindsight would've been easier to pull at least the upper intake plenum off then soak, pressure wash, repeat.

Then spent a couple of hours cleaning the EGR valve (taken off the intake), also clogged with carbon.

Ditto again for the Throttle Body, IME to clean it completely easier to take it off the intake and work on it at the bench to remove the baked on sludge and carbon in the throat, vacuum ports, butterfly, IAC port/passageway, etc,etc.

If you do this job plan ahead with new Toyota Vacuum hose and the sections of small diameter coolant hose, TB gasket, ---. And while the TB is off, might as well replace the valve cover gasket, spark plug tubes, both breather hoses, and PCV grommet if they're due.

Amazing how clogged up everything can get after 20-25 years.

 

[jatree]

As someone who went through this (and thinks he is done), one of the most common culprits is the EGR VSV - if your mechanic didn't replace that, I'd start by testing it. Lot of info available on it including here Checking VSV for EGR easy way P0401 - https://forum.ih8mud.com/threads/checking-vsv-for-egr-easy-way-p0401.211364/

 

[leonard_nemoy]

I started down this rabbit hole just to realize that the aftermarket exhaust manifold on my rig was the cause of my P0401. Fixed it with a scan gauge lol.

Just making sure you don't have an aftermarket header.....

 

[FreedomRider]

As others have said... get a scan gauge tool, get a Bluetooth odb2 reader, have the manifold cleaned by a pro. You’ll figure it out. Mine was cleaning the manifold out professionally but you can do it yourself too. And that was after replacing a bunch of parts and all I needed to do was clean the upper manifold....

Thank you and everyone very much for your time, guidance and experience
I am going to have the manifold cleaned professionally by a Toyota pro this Friday and will let everyone know the results. God Bless

 

[FreedomRider]

I started down this rabbit hole just to realize that the aftermarket exhaust manifold on my rig was the cause of my P0401. Fixed it with a scan gauge lol.

Just making sure you don't have an aftermarket header.....

Hey Leonard ! Thank you so much for this input. I will ask the Toyota technician to validate the exhaust manifold. Best Regards, Joe

 

[davidrh]

My 1996 throws it twice every time I drive from Colorado (11,000') to Texas (600'). Very rare other than that so I reset it and forget it.