Engine Threw a CEL - P0401

Threw a CEL - P0401

Well I was driving around today and threw a CEL on my 96. I scanned it with my buddy's OBDII scan tool..

So.. anyone ever experenced this before? I take it that I need a new EGR valve? Any ideas?

whats it saying it is? my car is throwing code 71(OBD1) which is my Exhaust gas temperature sensor, also part of the EGR system

That's the only info it's giving me.. Scanned it with the tool, went to it's website canobd2.com, entered the error code, and got that.. I cleared the code, hopefully it dosen't come back. Meanwhile I'm checking all the vac hoses that goes to the EGR valve.. POS EGR, uber useless.

Yeah, sounds like a issue with the EGR valve either sticking or not opening enough due to carbon build up. Vaccum lines would be the first thing I woudl check - then it would be to take the EGR valve off (PITA) and check it for carbon build up. I would recommend getting another valve - last time I had to change that on a 7AFE and 5SFE engines, they were so caked up with deposits, was nearly impossible to completely clean out.

theres a VSV under the throttle body id test and look at that aswell..

im thinking of making an egr blockoff plate, but im gonna have a CEL all the time though

excuse my ignorance but whats a VSV?

my idle is at 3k everytime i turn the car.....does this have anything to do with it??? what vaccum lines should I look at?

VSV = vaccuum switching valve 2 vacuum ports and an electrical connection


for a fast unstable idle i recomend cleaning the throtle body and the IAC idle air control valve take the throtle body off and give it a thourough cleaning

I think I might have to do the same.. my idle is really f*ed up during cold starts. rough/unstable idles in neutral, and vibrations.

Anyways the CEL came back on the next day.. I'm going to clean the TB this weekend and see if I can salvage th e EGR valve.. Do i need a new TB > intake manny gasket?

i have reused those gaskets a few times just make sure there in good shape.

my car has 243k on it and its running top notch the throttle body seems to mess alot up when its not quite right

I only have < 109K right now so the engine should still have plenty of life to it

I hear of some people talk about "adjusting the idle." Is that just fiddleing with the throttle cable or is there something else to it?

that means adjusting the the idle screw. its a screw that adjusts the air intake into the TB with no throttle application. when the TB heats up the little piece expands and restricts the air intake into the manifold

I had the same problem before. My idle shot up to 2000RPM and would bounce from 1500 to 2000 RPM at idle. I had the same check engine code. I took it to Toyota and they found out that the hose to the PCV EGR whatever thingy was torn. They replaced that hose for $49.95 and my problem was fixed.

Should be a $10 fix if you DIY.

where the EGR thing? pics??

is that the 98 model ?

nope, 96-97 1.8L 7A-FE. If your car is california emmisions, I would replace it like the one you have, unless is the same as federal emissions. I would port and polish the new throttle body if you need another one.

Check the autozone website or a haynes manual.

I finally got a chance to work on the car today.. took off the EGR valve, modulator, and VSV..

Most people I spoke to say it's usually the VSV that goes bad but I tested it with a OHM meter and it was within specs. I got some carb/choke cleaner and clean out the EGR valve even tho there is no visable signs of blockage.. but the thing was all sealed up, i'm not sure if it is possible to take it apart. I couldn't do any real testing because I dont have a vacumm pump with a gauge (and harbor freight was sold out).. but I did all that I can do for now and clear the CEL. Lets see if this solves anything.

nuts.. it came back on today.

okay, here's my results for the code po401. there is a VSV in the tank(gas) that is erratic. the part costs about $80. hopefully the dealer fixed the problem. this is for the 8th gen corolla(my wife's car is a 99). hope this helps everyone with the same code. peace

chris

kinda late..

i know it is, just wanted to help out others because they never did say if they got their codes fixed or not. do you have anything else to say or contribute to help others? thank you kindly.

chris