Cheatin' the OBD2 test.

[BSeward]

I've got a 2002 Lanos - 83,000 miles. Car runs great, but the CEL is on, and it is a problem in the EVAP system.
I've been getting the car to pass emissions in NY State by clearing the codes, either with a code checker, or disconnecting battery. Evidently the EVAP will not test if the fuel level is over 85%, so I just keep the tank filled (like every 25 miles or so...) for about 100 miles. This will let every sensor but the EVAP test. New York allows one sensor to read not ready on a 2002 car. Everything else works fine, and this gets me through the inspection - and has for the last 3 years. It's due again, and I'm going to try to sneak it through the same way.

Last winter, I kept the tank full - literally filing it daily - just to see what would happen with the CEL. After a few days, the light went out, and stayed out till I let the fuel level drop to about 3/4 tank.

The offending code was something concerning p0446 Any ideas or comments??

[Trey05Woo]

Hey there nice to see a fellow new yorker on the site. Im a nycer myself born and raised (queens) though relocated to miami, fl for 7 years now...

Anyways on to your problem and its a fairly easy one. Unfortunately though, all checks done to the system can only be performed with a scan tool which allows system tests and displays engine data.

All the EVAP system does is feed the excess vapors in the fuel tank to the engine. The components which make up the system are
Purge Valve found at the rear of the engine mounted on the intake manifold support bracket
EVAP canister found at the right rear underside of vehicle
Mini Charcoal Canister found mounted on the fire wall behind the engine
Fuel Tank Pressure Sensor found on the output line from the tank which feeds the canister
various plastic lines and rubber vaccum connects
Vent solenoid found at the canister under car

How the system works: basically fuel releases vapors especially as the liquid fuel level in the tank diminishes. These vapors are harmful to the enviornment so they are collected and fed to the engine. The pressure sensor detects a certain value, the pcm commands the vent and purge solenoid on. The system is connected to the engine via vaccum lines. With the solenoids on, the engine is allowed to apply vaccum and suck these vapors into the intake manifold. The computer monitors these vaccum readings, with the solenoids on (open) and off (closed). 0446 (EVAP sys vent control malfunction) sets because the pcm detects no difference in vaccum readings after said function. This can be due to a bad vent or purge solenoid. Clogged or plugged vaccum line or canister.

The code will only set with fuel level between 90-15%, and if you disconnect the battery the fault has to occur TWICE for it to set and light the CEL. So try taking it in with a full tank or empty, and disconnect the battery right before they scan it. This will also erase history codes. It might just pass, but I would advise you to try and get it fixed. If the system cannot vent properly tank pressure will vent through the emergency vent on the fuel cap. You are basically vent $$$ into the atmosphere...

[Daniel]

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0446 (EVAP sys vent control malfunction) sets because the pcm detects no difference in vaccum readings after said function. This can be due to a bad vent or purge solenoid. Clogged or plugged vaccum line or canister.
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If the system cannot vent properly tank pressure will vent through the emergency vent on the fuel cap. You are basically vent $$$ into the atmosphere...

Can a P0446 code be throwed by a non air-tight fuel cap?

[Trey05Woo]

No, a loose or bad fuel cap will set a leak or system performance code.

0446 is strictly a ventilation (feed) malfunction in the system.

Usually the culprit is the purge valve which goes bad. It sends a pw signal which the ecm uses to monitor sys vaccum.

However, due to his location (cold/snow), its very likely the canister undercarriage is beat to hell...