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…