← Back to list

2001 Chevy Cavalier P0440 EVAP Fault: How to Fix Harness, Gas Cap, and Cracked Filler Neck

Model: 2001 Chevy Cavalier Fault Code: P0440 Posted: 2008-03-28 07:51

ratpower396 wrote: Can someone please help me locate the EVAP harness on my 2001 Chevy Cavalier so I can inspect it? Thank you. The EVAP harness is typically located under the rear of the vehicle, on the passenger side near the right rear wheel and close to the rear axle. There are usually two wires running there, and the purge canister is also in that area. Note: Even after replacing components like the gas cap, purge solenoid, charcoal canister, and having a smoke test performed, some owners still experience P0440 code issues. A common but overlooked cause is a crack in the plastic insert inside the filler tube (the metal tube where the fuel filler nozzle connects). This crack allows vapor leakage, triggering the EVAP system fault. One user found that applying epoxy to the cracked plastic insert resolved the issue—though the light did not go off immediately. Another reported that even after a professional smoke test by Firestone, the crack was missed because the testing adapter only engaged the outer metal portion of the filler tube and didn't inspect the internal plastic insert where the crack occurred. For owners with a 2001 Chevy Cavalier experiencing P0440 code, it's recommended to first check the EVAP harness and filler neck. If no issue is found there, closely examine the filler tube for cracks in the plastic insert. Repairing this with epoxy may resolve the problem temporarily. However, if the issue persists or worsens, a dealer diagnosis (costing around $100) has confirmed that a cracked filler neck is a common root cause. If replacing the plastic insert is needed, it appears to be a press-fit component and may not be available as a standalone part—making replacement difficult without specialized tools or parts.

Related fault codes
P0440
Comments (8)
Anonymous 2008-03-28 12:23

Thanks for the location! I’ll check that area first. By the way, what pressure should a proper gas cap hold? Is there a standard value?

Anonymous 2008-03-28 12:40

I tested my gas cap with a cut wire and found no pressure—this suggests a leak. After replacing several EVAP components including the gas cap, purge solenoid, and charcoal canister, the P0440 code remained. I later discovered that the plastic insert inside the filler tube had a crack. Applying epoxy fixed it temporarily—the check engine light turned off after a few drives.

Anonymous 2008-03-28 18:50

I found two plugs near the air filter, but neither matches the expected 2-wire EVAP harness. The ones I found are covered by the filler cap and vent hoses—so they might be inaccessible or not part of the main system.

Anonymous 2008-04-17 06:10

I had a P0440 issue after replacing multiple parts: gas cap, purge solenoid, purge valve, and charcoal canister. The smoke test didn’t catch it. Upon closer inspection, I found a crack in the plastic insert inside the filler tube—this is where the fuel nozzle connects to prevent backflow. After sealing it with epoxy, the check engine light went off. I’m still baffled as to why Firestone’s smoke test failed to detect this flaw.

Anonymous 2008-04-17 06:36

The smoke test seems to target only the outer metal portion of the filler tube and the lines connected to the canister. The plastic insert is inside the filler tube, where the gas cap screws in—this area is not fully exposed during testing. Since the crack was internal, it wasn’t visible or detectable by standard methods. This raises concerns about how smoke tests evaluate seal integrity.

Anonymous 2008-04-25 08:27

Smoke tests typically focus on the filler tube and associated lines. The adapter used in testing may only grip the outer metal sleeve of the filler tube, not the internal plastic insert where the crack occurs. This means the leak point remains hidden—especially since the gas cap screws into the plastic insert, which can become compromised over time due to vibration or age.

Anonymous 2008-07-10 08:14

I own a 2001 Chevy Cavalier and recently got a P0440 code. I checked the harness—seems fine—and inspected the filler neck, where I found a crack. After epoxying it, the light didn’t go off immediately. I took it to the dealer for diagnosis at $100—they confirmed it was a cracked filler neck (doh!). I’ll try more epoxy first, but if that fails, how do I replace the plastic insert? It appears to be pressed in—can I just remove and replace it? I haven’t found a standalone part yet.

Anonymous 2008-07-10 17:16

Is the plastic insert available as a separate replacement part? I suspect the filler neck is sold as an integrated unit, so replacing only the insert might not be possible without special tools or aftermarket parts.