Passing Emissions Inspection with MIL On

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Sep 2, 2007
Brooklyn, NY
My car, a 1997 Toyota Avalon, has the check engine light on due to an evaporative emissions code (P0446). I took the car to the mechanic and he blew out the charcoal canister and main canister with air and reinstalled it, and reset the check engine light. It came on again 3 days later with the same code. Now my question dilemma is, I do not want to spend a ton of money for this little stupid problem, as the car is 12 years old, but I need to pass inspection. Is it possible to reset the check engine light and then take it to the inspection station and have it pass? Would I need to disconnect the battery cable for a few minutes to reset everything? Any help is appreciated, THANKS!
My last emmission check was done while the CEL had been on solid in my car for the previous 3 months or so. I got the best results I've ever seen on any car.

They noted it on the print-out, but said it obviously had nothing to do with the emmission system on the car.
Until you drive it around a bit, it won't pass. A 1997 vehicle would be OBD II, so just unhooking the battery won't erase codes but it will reset the operating parameters. I don't know how NY does testing, but I thought most testing stations now used a scan tool on the OBD II vehicles and didn't use the treadmills. I think the answer is you will most likely fail once they plug in the scan tool and find that either you have codes stored, the operating parameters haven't been learned yet, or your light is on.
Resetting the codes also resets all of the emissions tests, so you'll fail if you do that. After resetting the codes, you generally need a couple hundred miles of regular driving for the tests to rerun, depending on your driving habits. You're going to need to either fix it or disable it in the computer if you can.
IIRC, you have like 3 chances to fix something to pass; then you get a pass if it cannot be fixed under a certain $ amount. as it is, you fail automatically w/ a emissions related code.
Yes, in NY the emissions testing is done via computer. I would like to avoid actually fixing the problem, since it will be very hard to track down the problem, will be very expensive, and does NOTHING for the drivability of the car. If there is a way to get around it, that would be very nice. They charge you $35 EVERY time in NY to inspect the car; pass or fail. I would like it to pass on the 1st time if possible!
In Maine you can have a couple IM monitors not ready and pass as long as the CEL is off. Seems like a compromise/ loophole.

DO NOT disconnect the battery or fuses as that will reset ALL the IM monitors and be a bigger flag. You can get cheap code readers for $30 that erase specific codes if they came back.

Part of GM's evap diagnostics are they won't run over 3/4 or under 1/4 tank of gas. Who knows how Toyota works but you could try buying gas every day.

I assume you've tried a new gas cap. Try a little glycerine on the o-ring to help it seal.
The gas cap seals fine as far as I know, the o-ring looks like new and whenever I open it up, it lets out a big "hiss"
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Sounds like a solenoid not letting pressure out.

In NYS you automatically fail for a CEL. I did pass after my battery died by spending an afternoon putzing around letting the computer run its tests. I had 1 emissions test not done, but you can pass with 2 not done. That's in the manual the NY DMV has online.

Either way, get the CEL looked at, and drive the car if you can.
Originally Posted By: Crashbox
I thought "MIL" stood for "mother-in-law"... Which may be quite appropriate if the light incessantly annoys you...

Originally Posted By: Crashbox
I thought "MIL" stood for "mother-in-law"... Which may be quite appropriate if the light incessantly annoys you...
I won't respond to that, I'll get shot.

Our county here in Ohio doesn't have emissions, but I ran STP injector cleaner (black bottle) and the CEL came on soon after. I kept an eye on it and my brother cleared the code for me. I asked a co worker about it (he sold cars for 20 odd years) and he said there probably was a piece of carbon worked loose from the cleaning, and it will go off. Sure enough, two days later it was off.
It depends on what the light it on for. If it is a misfire and the engine is running rich, it isn't passing!
Originally Posted By: parimento1
The gas cap seals fine as far as I know, the o-ring looks like new and whenever I open it up, it lets out a big "hiss"

Don't assume this. I've replaced two caps on both my jeeps. They both looked just fine. I typically get two codes. One is for a minor evap leak ..that's just a pending code (IIRC). If it goes through two "good trips" it then sets the CEL/MIL

The FIRST thing you do when you get an evap code is replace the gas cap. The avoided costs in the unlikely event of a malfunction in the rest of the evap system makes it the cheap thing to do.

You may be able to trump the emission test. In PA, and I assume elsewhere, you're allowed for one (or maybe two) of the "readiness" states to be "un-ready". The evap system on many models doesn't function with too full a tank or too empty a tank.

A "good trip" is defined by the PCM ..but may require two or more cold starts. It may not JUST be driving it for xxx miles.

I had to go through this with my son's 00 Cherokee. He has 3 cats and 4 sensors. They had some issues with the cats and it is (or was) a $750 repair. The tech, I know him, plugged it in and said "no way. None of the parameters are met". I then kept driving it and taking it in to pass. He explained that you were allowed one parameter not to be set. That meant that the O2 sensor heater circuit readiness routine didn't need to be complete IF the fuel EVAP purge had done its thing. It could not do that with a full tank. Drove it to the point if 1/2 tank ..reset the PCM..went through a cold start and drove it about 12 miles ....praying that the O2/cat check wouldn't expire.


Fill up the tank and try it again.

..and change the cap.
I'm sorry, but I've just got to laugh at most of these responses. How in the world is the P0446 - Vent Control Circuit Low going to be caused by a bad gas cap? If he's getting a hissing, it's obviously sealing. I don't know anything about Toyota's setup, but it sounds to me like a bad vent solenoid/clogged canister, which would also leave the tank under negative pressure, resulting in the hissing you're talking about.
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The mechanic blew compressed air thru the canisters and stuff so I don't think its a clogged canister. All the passages passed air thru fine, even when one side was held closed, it came out the other. The vent solenoid might be it, since P0446 is the circuit malfunction. my friend has a code scanner, im gonna try and erase it, then fill it up with gas, and see how long it stays off for. If that doesn't work, I called another mechanic who I go to and he has the special scan tool for emissions, etc.
Even if the code is erased, the computer has a memory to show it was RECENTLY erased. This tells the emissions tester that it was recently cleared, and the problem may still be there.
It is a safety back up to make the codes valid at the testing station.
sometimes up to 50 starts are needed .
In other words, it has to be fixed. Vacuum lines are critical, and the electronic valving has to work.
If your canisters were loaded with fuel, blowing them out does not fix the problem.
It's the same as a boat in the ocean with a hole in the bottom. bailing the water out will not fix the hole.
In my state, I remember they will hook up a scanner to my 96 sunfire. they check for gas cap leaks. I remember one guy didn't do a tailpipe sniffer when my car didn't have any codes last year.
I'm sorry, but I've just got to laugh at most of these responses. How in the world is the P0446 - Vent Control Circuit Low going to be caused by a bad gas cap?

Laugh away
I didn't see (though it surely could have been there) what the code was (as in meaning) and I didn't bother to look it up. I said in my laughable post, the EVAP PURGE protocol may not occur if the tank is full or close to empty.

No MIL/CEL ...badge.

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