Evaporative Emission System Leak (small)
Indicates a small leak in the evaporative emission system.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer is detecting that there’s a minor leak in the vapor hoses or fuel system that lets fuel vapors escape into the atmosphere.
What the computer is actually seeing
The Engine Control Module (ECM) monitors the evaporative system pressure when the engine is off. If it sees a drop in pressure below a certain threshold (typically around 0.5 inches of water column), it triggers this code, indicating a leak.
What a healthy reading looks like
The expected pressure in the evaporative system when sealed should be around 0.5 to 1.5 inches of water column when tested.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the gas cap: Ensure it's tightly sealed with no cracks. Clear the code and see if it returns. Decision: If code returns, proceed to next step.
- 22. Inspect the vacuum hoses: Look for cracks or disconnections. Use a smoke machine if available to test for leaks. Decision: If leaks found, repair hoses. If no leaks, move to next step.
- 33. Check the purge valve: With the engine on, check if the purge valve is operating correctly. It should close when not commanded. Decision: If faulty, replace the purge valve. If operating correctly, check the next step.
- 44. Test the fuel tank pressure sensor: Use a multimeter to verify the sensor resistance (should be around 5.0 to 10.0 ohms). If out of spec, replace it. If within spec, the issue may be intermittent or require further testing.
Common causes
- Loose or damaged gas cap
- Cracked or damaged vacuum hoses
- Failed purge valve or vent valve
- Faulty fuel tank pressure sensor
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but address it soon to prevent potential emissions fines.
Will this code return after clearing?
It may if the underlying issue isn't fixed.
Why does this code sometimes pair with SPN 0441?
SPN 0441 indicates a large leak, usually due to similar issues in the system.
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