# PO440 code in 01 Chevy Impala

**URL:** <https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256>\
**Category:** Maintenance/Repairs\
**Tags:** impala\
**Created:** [February 5, 2008, 1:36am UTC](https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256 "2008-02-05T01:36:51Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![lprocter](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/lprocter/32/40_2.png) [@lprocter](https://community.cartalk.com/u/lprocter)\
**Post date:** [February 5, 2008, 1:36am UTC](https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256/1 "2008-02-05T01:36:51Z")

</div>

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?

---

<div class="post-metadata">

**Author:** ![Roadrunner](https://avatars.discourse-cdn.com/v4/letter/r/d2c977/32.png) [@Roadrunner](https://community.cartalk.com/u/Roadrunner)\
**Post date:** [February 5, 2008, 2:02am UTC](https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256/2 "2008-02-05T02:02:53Z")

</div>

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.

---

<div class="post-metadata">

**Author:** ![lprocter](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/lprocter/32/40_2.png) [@lprocter](https://community.cartalk.com/u/lprocter)\
**Post date:** [February 5, 2008, 3:38am UTC](https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256/3 "2008-02-05T03:38:54Z")

</div>

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.

---

<div class="post-metadata">

**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\
**Post date:** [February 5, 2008, 4:10am UTC](https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256/4 "2008-02-05T04:10:08Z")

</div>

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](http://www.alldata.com). Or, you can get a subscription to alldata for $25. Or, you can buy the service manual for over $100.

---

<div class="post-metadata">

**Author:** ![Roadrunner](https://avatars.discourse-cdn.com/v4/letter/r/d2c977/32.png) [@Roadrunner](https://community.cartalk.com/u/Roadrunner)\
**Post date:** [February 6, 2008, 5:57am UTC](https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256/5 "2008-02-06T05:57:30Z")

</div>

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

---

<div class="post-metadata">

**Author:** ![lprocter](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/lprocter/32/40_2.png) [@lprocter](https://community.cartalk.com/u/lprocter)\
**Post date:** [February 6, 2008, 5:18pm UTC](https://community.cartalk.com/t/po440-code-in-01-chevy-impala/10256/6 "2008-02-06T17:18:59Z")

</div>

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