After driving with the 0401 light on since I bought it, Its finally cleared!
I know there are a million of these but I thought I should share
For the last four years I' been clearing the code with the scangauge before getting the smog test and it has never been a problem until now. The same place wouldn't pass it this time because the computer wasn't on "ready mode". I don't know why it wasn't a problem before. I doubt the test operator can bypass but I'm not sure.
Some of the tests and procedures in the FSM seemed complicated and required the throttle body and intake to be removed. So, following the many threads on the subject I was able to easily find the problem which was the VSV and replaced it without removing half the engine. Wasn't super easy and my hands got a little scratched but made it!
As per some of the threads the main culprits are the VSV, Modulator, clogged orifices and then gas temp sensor or EGR.
-First I decided to check the easy access parts and the most talked about is the orifice that goes through the air intake. I was under the impression that it was pretty deep and used a long welding wire. Thought I hit a blockage and pushed it hard (S#@& !), is only about three inches and then you poke a hole through a hose on the underside and when tried to replace it, the hose broke and the tip stayed on the nipple in the hardest most hidden part of the intake under side.
Anyway, orifice was fine so checked continuity on the gas temp sensor right by the orifice and it checked fine.
-Next was the modulator which was tested by following one of the thread which I couldn't find again but it is a lot easier than FSM. It easily comes out by removing the hoses and you can blow and suck on the bottom nipple to check for suction or resistance of the diaphragm. It checked fine so I cleaned the felt filter by just removing the top cap and checked for air when you blow on the side nipple while covering the two on the opposite side. Air should go through the filter.
-Lastly it was on to the VSV. The FSM asks for removing air intake to check resistance and to blow on one side and for it to come out the other side. Then, by connecting 12 volts directly it should close and air would come out of its filter instead of the opposite side.
One of the threads pointed at the harness sitting on the front side of the throttle body To perform both test without removing it (Thank you MUD). The harness has four wires but the two yellow opposite wires on top go to the VSV and it can be tested without removal (assuming those wires are OK)
I didn't even have to do the second test. There was no continuity at all.
FSM "Resistance: 37 − 44 Ω at 20°C (68°F) If there is no continuity, replace the VSV."
So because I'm lazy I decided to remove it without removing air intake or throttle body. First removed the modulator and the top bolt of the long intake bracket on the driver side. The bottom bolt was only loosened with a swivel breaker bar and a short extension from under the vehicle.
Then by undoing the one bolt visible from the underside (about 30" of extensions) and the other through the driver side from the top with a gear wrench, the VSV was lose. Easier said than done though. Both where pretty tight so had to find a 6 point socket because the 12 point was damaging the heads and then had to deal with the hoses.
My hands where a little scratched but after a couple hours including the time consuming mishaps, it was all done. (Putting everything back probably took only 15 min)
Hint. (Bolts are not actually that hard to reach. To make it easier when installing VSV back, I kind of aligned it and used the bolt from underneath with the extensions to push and drive it into it's hole. That made installing the other bolt much easier)
Take into consideration that I'm a mechanic.
I've gone through the test cycle a couple times and it hasn't come back so far. Scangauge shows all clear and ready
On a side note, Napa doesn't carry the right size vacuum hoses even though a friend at the dealer said that they get their hoses there for the used vehicles. Had to order a piece of I believe two feet for about $18 from Toyota . It is much nicer and heavier duty than what Napa and other auto parts have.
I know there are a million of these but I thought I should share
For the last four years I' been clearing the code with the scangauge before getting the smog test and it has never been a problem until now. The same place wouldn't pass it this time because the computer wasn't on "ready mode". I don't know why it wasn't a problem before. I doubt the test operator can bypass but I'm not sure.
Some of the tests and procedures in the FSM seemed complicated and required the throttle body and intake to be removed. So, following the many threads on the subject I was able to easily find the problem which was the VSV and replaced it without removing half the engine. Wasn't super easy and my hands got a little scratched but made it!
As per some of the threads the main culprits are the VSV, Modulator, clogged orifices and then gas temp sensor or EGR.
-First I decided to check the easy access parts and the most talked about is the orifice that goes through the air intake. I was under the impression that it was pretty deep and used a long welding wire. Thought I hit a blockage and pushed it hard (S#@& !), is only about three inches and then you poke a hole through a hose on the underside and when tried to replace it, the hose broke and the tip stayed on the nipple in the hardest most hidden part of the intake under side.
Anyway, orifice was fine so checked continuity on the gas temp sensor right by the orifice and it checked fine.
-Next was the modulator which was tested by following one of the thread which I couldn't find again but it is a lot easier than FSM. It easily comes out by removing the hoses and you can blow and suck on the bottom nipple to check for suction or resistance of the diaphragm. It checked fine so I cleaned the felt filter by just removing the top cap and checked for air when you blow on the side nipple while covering the two on the opposite side. Air should go through the filter.
-Lastly it was on to the VSV. The FSM asks for removing air intake to check resistance and to blow on one side and for it to come out the other side. Then, by connecting 12 volts directly it should close and air would come out of its filter instead of the opposite side.
One of the threads pointed at the harness sitting on the front side of the throttle body To perform both test without removing it (Thank you MUD). The harness has four wires but the two yellow opposite wires on top go to the VSV and it can be tested without removal (assuming those wires are OK)
I didn't even have to do the second test. There was no continuity at all.
FSM "Resistance: 37 − 44 Ω at 20°C (68°F) If there is no continuity, replace the VSV."
So because I'm lazy I decided to remove it without removing air intake or throttle body. First removed the modulator and the top bolt of the long intake bracket on the driver side. The bottom bolt was only loosened with a swivel breaker bar and a short extension from under the vehicle.
Then by undoing the one bolt visible from the underside (about 30" of extensions) and the other through the driver side from the top with a gear wrench, the VSV was lose. Easier said than done though. Both where pretty tight so had to find a 6 point socket because the 12 point was damaging the heads and then had to deal with the hoses.
My hands where a little scratched but after a couple hours including the time consuming mishaps, it was all done. (Putting everything back probably took only 15 min)
Hint. (Bolts are not actually that hard to reach. To make it easier when installing VSV back, I kind of aligned it and used the bolt from underneath with the extensions to push and drive it into it's hole. That made installing the other bolt much easier)
Take into consideration that I'm a mechanic.
I've gone through the test cycle a couple times and it hasn't come back so far. Scangauge shows all clear and ready
On a side note, Napa doesn't carry the right size vacuum hoses even though a friend at the dealer said that they get their hoses there for the used vehicles. Had to order a piece of I believe two feet for about $18 from Toyota . It is much nicer and heavier duty than what Napa and other auto parts have.
Last edited: