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2002 Chevrolet Trailblazer P0440 and P0420 Codes: EVAP System Leak & Catalytic Converter Issue - How to Fix?

Model: 2002 Trailblazer Fault Code: P0440 Posted: 2007-10-11 08:07

I've been researching this forum for months trying to resolve a persistent issue with my 2002 Chevrolet Trailblazer V6 Vortec (103,000 miles, well-maintained). I'm a female owner and very particular about car maintenance—regularly replacing plugs, boots, fuel filter, fuel pump, and even installing a direct-fit catalytic converter. The problem started when my fuel pump failed in Texas. After replacement, I drove 100 miles before the SES light came on. The dealer scanned it and found code P0440 (EVAP system malfunction). I replaced the cat, but just 20 miles later, the same P0440 code returned. A smoke test showed no leaks—so they confirmed there's no vapor line issue. The day before yesterday, while driving onto the interstate near my home, the truck suddenly shut off. It cranked back up, but when I tried to leave, it made a grinding noise and wouldn't turn over at all. I called roadside assistance, which towed me to the dealer. They reported new codes: P1633 (related to the engine control module) and P0440/P0420. The dealer initially suggested my relay box was loose—after spending $150 tightening it, the P0440 code remains. I'm now extremely concerned about driving this vehicle with my husband deployed again, especially given how many times we’ve been stranded. I love this truck and don’t want to lose it. I've spent nearly $700 on repairs since January and feel like many shops are just throwing parts at the problem without a proper diagnosis. I'm at my wits' end—any advice or insight would be deeply appreciated. Thanks in advance for your help! P.S. I’ve learned that some dealers offer warranties on catalytic converters, especially if they’re verbally confirmed and signed on receipts.

Related fault codes
P0420P0440
Comments (3)
Anonymous 2007-10-11 08:23

The P0440 code indicates an issue with the EVAP (Evaporative Emission Control) system—designed to capture fuel vapors from the tank and re-introduce them into the engine for combustion, rather than releasing them into the atmosphere. A technician should be able to identify a leak in this system. The P0420 code suggests the catalytic converter is not performing efficiently, which may point to a faulty or low-quality converter. If you're experiencing repeated P0440 codes after replacing the cat, it's likely either a poor installation, a defective part, or an underlying EVAP leak. Take your truck back to the shop and ask if they will honor their warranty on the catalytic converter—especially since you were told one existed. A quality converter should not cause repeated emissions faults.

Anonymous 2007-10-11 08:31

Thanks for the response! The SES light is driving me crazy, especially given how often we travel with our family while stationed away from home. I’ve now confirmed that the dealer verbally mentioned a one-year warranty on the catalytic converter and I’ve asked them to write it down and sign it—this has helped me feel more confident about my repair choices.

Anonymous 2007-10-11 08:45

Exactly—take it back to the shop and ask for a warranty on the catalytic converter. If they warned you about potential performance issues or poor quality, that’s a red flag. A reputable shop should stand behind their work and offer a warranty if there's a known risk of failure.