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2003 Dodge Neon SE 2.0L P0440 Code Appears After Fuel Fill-Up - Common Causes & Fixes

Model: 2003 Dodge Neon SE 2.0L Fault Code: P0440 Posted: 2012-02-25 19:41

My 2003 Dodge Neon SE with a 2.0L engine and approximately 96,000 miles is currently displaying the P0440 diagnostic trouble code, which activates the Check Engine Light (CEL). The code typically appears right before or immediately after I refill my fuel tank. After noticing this pattern, I reset the light and ensure the gas cap is tightly secured—having already replaced it. Recently, I've tightened the cap to three full clicks (with audible clicking) each time the code appears. Previously, the vehicle showed P0456, which has since resolved after the new cap installation. I refill my tank weekly, coinciding with when the P0440 error occurs. While I’ve inspected all visible EVAP system components—including fuel lines, NLVD assembly, and purge canister—for cracks or damage, no issues were found. There is also no detectable gasoline odor. Given this, I’m wondering whether the issue stems from a loose gas cap or if a more expensive component—such as the leak detection pump—is at fault. The recurring timing suggests a connection to fueling activity. Any insights into possible root causes would be greatly appreciated.

Related fault codes
P0440
Comments (7)
Anonymous 2012-02-26 09:54

A new OEM gas cap from your local dealership is worth trying—aftermarket caps can vary significantly in quality and sealing performance.

Anonymous 2012-03-19 10:24

I have the exact same issue as user bkim1550. Did anyone find a solution besides replacing the gas cap? Any advice would be helpful.

Anonymous 2012-03-20 04:59

The most common cause of P0440 in vehicles like the 2003 Dodge Neon SE is either a faulty or degraded gas cap, or a malfunctioning leak detection pump.

Anonymous 2012-03-20 06:14

Thank you for the input. I'll update everyone on any further developments.

Anonymous 2012-04-19 11:42

It was the gas cap. After tightening it to three clicks after my last fuel fill-up, the Check Engine Light disappeared and hasn’t returned in over three weeks. This has been a consistent issue for nine years—never before did it occur. I suspect the rubber seal dried out over time, though I’ll keep an eye on it moving forward.

Anonymous 2012-04-19 11:50

Jeff, thank you—I almost forgot to say thanks!

Anonymous 2012-07-11 15:13

My wife recently purchased a 2003 Dodge Neon SXT with the 2.0L engine and it started showing a P0440 code. We replaced the gas cap, but the error returned. A professional smoke test revealed a cracked EVAP canister. After installing a new one, the code reappeared after refueling. The mechanic performed another smoke test and discovered that the fuel sender unit on top of the fuel tank also needed replacement. This was the final fix.