What does code P0440 mean on a Buick and is it safe to drive?
P0440: Evaporative Emission System Control System Malfunction. Here’s what it means on your Buick, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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What this code means
A general fault in the EVAP system—could be a leak, stuck valve, or sensor issue.
Common causes for your Buick
- Gas cap loose or faulty
- Purge or vent valve stuck
- Charcoal canister or hose leak
Symptoms
- Check Engine Light
Typical fixes
- Replace gas cap
- Test purge/vent valves
- Smoke test EVAP system
Repair cost range
For a Buick, repairs for P0440 often fall between $20 and $400, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.