What Does P0440 Mean?
A general malfunction has been detected in the evaporative emission control (EVAP) system. This is a broad code indicating the PCM found a problem during the EVAP system self-test but is not specific about whether it is a leak, purge flow issue, or vent problem. The system is designed to capture fuel vapors from the tank and route them to the engine for combustion. The driver may notice a fuel smell and the MIL will be on.
Common Causes
30%
Loose, damaged, or missing fuel cap
25%
EVAP canister purge valve stuck open or closed
20%
Cracked or disconnected EVAP hose or line
15%
Faulty EVAP canister vent valve
10%
Charcoal canister saturated or damaged
Diagnostic Steps
1
Check the fuel cap — remove it, inspect the gasket for cracks or damage, reinstall with a firm click, clear the code, and drive through a complete EVAP monitor cycle to see if the code returns.
2
Perform a smoke test on the EVAP system by introducing smoke through the EVAP service port — watch for smoke escaping from hoses, connections, the canister, or the fuel tank area.
3
Command the purge valve on and off via the scan tool and listen for a click. Measure vacuum at the purge valve outlet when commanded open — vacuum should be present with the engine running.
4
Command the vent valve closed and verify the EVAP system can hold pressure/vacuum — a rapid loss indicates a leak in the sealed system.
5
Inspect all EVAP hoses and vapor lines from the fuel tank to the canister and from the canister to the intake manifold for cracks, disconnections, or damage.
Estimated Repair Cost
$20 - $500
Parts + labor, varies by vehicle and location
A general malfunction has been detected in the evaporative emission control (EVAP) system. This is a broad code indicating the PCM found a problem during the EVAP system self-test but is not specific about whether it is a leak, purge flow issue, or vent problem. The system is designed to capture fue...
The most common cause of P0440 (Evaporative Emission Control System Malfunction) is: Loose, damaged, or missing fuel cap
Typical repair costs for P0440 range from $20 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. The EVAP system captures fuel vapors, so a malfunction may result in minor fuel odor. No performance impact. Fuel consumption may increase very slightly. Required for emissions compliance.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0440 to identify the root cause.
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Quick Info
Category
Powertrain
System
Evaporative Emission (EVAP) System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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