PO440 code in 01 Chevy Impala

Recently, over the past week or two, when my parents have been driving my 01 Chevy Impala (3.4l V6, 96,000km), the CEL has come on, Using a scan tool, the code pops up as PO440, which is Evaporative Emissions Control System Malfunction. So, my question is: What could cause this (and it’s not a loose gas cap - there’s a separate code for that), and secondly, what’s the most likely cause?

Code PO440 is the generalization number for the system.

Have you or your parents (and I ask this respectively) been ‘topping off’ the fuel tank when refueling?

It IS possible the charcoal canister has become saturated and MAY need replacing.

Another component is a (faulty) purge valve in this system which releases fuel vapors into the air intake to be burned off.

With access to a hoist (or a jack and safety jackstands) and a Haynes repair manual this system can be easily checked out and faulty components replaced as necessary.

I never top off the gas tank to avoid charcoal canister problems, and I always remind my parents to never top it off either - they respond by just not buying gas… oh well.

There are troubleshooting charts to follow for DTCs (Diagnostic Trouble Codes), such as P0440, at your public library, if it has a Web subscription to www.alldata.com. Or, you can get a subscription to alldata for $25. Or, you can buy the service manual for over $100.

OR, he can take it to OKs shop in Oklahoma and let him fix it!

Road trip!! I’ve always wanted to see Oklahoma… and bask in OK4450’s expertise…