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P0446 Code in Buick Regal


Four times now, my car has shown code P0446 - Evap control system. I have had the catalytic converter replaced, the purge valve replaced and a new gas cap. Check engine light stays off for a few days between these repairs and now is back on again… suggestions?

What Is The Condition Of The Filler Neck Where The Gas Cap Seats Against It?

Has the cap’s seat checked for corrosion? Do you live in the rust/salt belt?

You don’t say what model year this vehicle is or how many miles on it, but I have seen corrosion problems in the area described above that even a new cap can’t overcome.

If it’s bad, try cleaning it (sanding - no sparks or debris getting in the tank). See if it can be smoothed. If it’s very bad, replacement may be necessary.


filter neck to gas cap ahs been checked and is fine… don’t live in the rust/salt belt.

Buick Regal LS with 113,000 miles

Something somewhat similar happend to me where my Suburban was throwing codes for a faulty EVAP system. One part was bad, replaced, but the CEL kept coming on, going away, back on. Turned out to be a bad electrical connection.

They also warned me that if I fill-up with the car running it could cause the code to go.

If you fill the tank past the first click, you may have saturated your charcoal canister. If this is the case, just don’t overfill your tank and the code will go away on its own.