P0401 dreaded code Fj80 (1 Viewer)

[johnnye23]

My Lx450 stays in Baja most of the time so my resources and tools are very limited. My Ca smog check was once again due and I had a CE light for code P0401 low flow egr.
This is what I did and light has not returned after driving many miles and fill ups.

I removed this vaccum line

Using a small wire I worked it up and down thru the nipple while spraying Wd40 into it. I then used a drill bit the same size as outter diameter of the vaccum hose and put a hole in the bottom of a aeresol cap and hung it above by a wire . Then I put the other end of vaccum hose back on the nipple. I started the engine and proceeded to pour water into the cap and the water was sucked into the engine slowly . I did this process about 4 times reset my CE light and it has been trouble free ever since.

 

[Kernal]

Something ain't right or I've lost my memory, or mind, whichever applies.

That small nipple or short pipe you sprayed WD40 into does not open into the intake manifold, it is a solid pipe that passes through the intake and comes out underneath where another hose connects to the EGR VSV switch. So anything you spray into that nipple goes into the switch IIRC?? Maybe it could then be sucked through the switch into the vacuum line on the other side of the switch?? Or, if the short hose on the underside of that pipe is not connected, than anything you put in the top will dribble out the bottom under the intake manifold.

Someone confirm or correct me please.

 

[jpoole]

Didn't read all of first post but yes @Kernal that's a pass-through port that connects to a soft/rubber vacuum line below the manifold which ultimately plumbs into to the EGR VSV valve.

The EGR VSV valve is open when unpowered, as I recall, and closed when powered and you can test that part of the plumbing pretty easily by powering/unpowering the vsv valve at the electrical plug for it (front of manifold near valve cover roughly). If the VSV section of the EGR system get's plugged up you are more likely to see a po402 (too much flow) as the VSV circuit is essentially always closed and vaccum can build to open the egr valve. If the VSV fails open then you'll see P0401, insufficient, because vacuum can't build up in the system to open the egr valve.

Other po401 causes related to no vacuum to open the egr valve could be leaks in the plumbing, clogged vacuum ports on the throttle body, failed or clogged vacuum modulator.

Best way to troubleshoot this system in my opinion is to start at the throttle body and work your way through. First, make sure the ports on the TB are both open and pulling a vaccuum. From there you can test the EGR valve itself pretty easily by pulling a vacuum on it to see if it makes the engine stumble at idle (when the egr valve opens). Once you know the system has vacuum and that the EGR valve opens/closes you can test the modulator and vsv valve and plumbing and should get the common/mechanical problems sorted that way. The vacuum modulator is one of the more common failure points.. etc.

Plenty of good info on toyota EGR troubleshooting online and on youtube. A decent vacuum gauge and other simple tools should be all that you need to do most tests.

 

[Kernal]

Roger all above.

@johnnye23 IME the major cause of that EGR code in this engine that happens over time is the build-up of carbon/varnish in all the ports related to the EGR system, then there's cracked or disconnected vacuum lines, then a stuck EGR valve (from carbon), or non-functioning vacuum modulator (from carbon), and then the large exhaust gas passageway that is cast into the upper intake can get plugged with carbon, and the Throttle Body and a few very small ports get clogged with carbon/varnish----. And then there may be a dead EGR VSV. Seems like the EGR temp sensor (almost) never fails.

So sometimes the best long term fix is to remove the Throttle Body and the upper intake plenum and clean them out completely (may need to hot tank the upper intake to clean out the tunnel that's full of carbon), and remove the EGR valve and test it, clean it, or replace it along with the modulator, then replace every vacuum hose in the system. You can buy the small diameter vacuum hose from Toyota in meter long (or longer) sections and cut to fit.

If you don't have a copy of the Factory Service Manual (FSM) you can download from this forum.

Try some searches for P0401, been discussed a lot in the past.

 

[jaymar]

For those with a smog test coming up in a hurry, ask when business is slow. Clear codes, drive at 60-65 for 20 or 30 minutes, back and forth on the freeway, clear any new codes and roll right up the testing station. That kills my 0401 and a few others every time. They're back the next day, though. And use a smog place that does free retests.

 

[johnnye23]

Thanks for the all the input. Whatever I did wrong fixed my issue luckily

 

[LC4LIFE]

I'd replace that heater valve while your in there digging around. That brownish plastic color is never good.