Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0440: EVAP System: Description
Powertrain Control Module (PCM) tests Evaporative (EVAP) emission system for a large leak. PCM monitors Fuel Tank Pressure (FTP) sensor signal to determine EVAP system vacuum level. When conditions for running are met, PCM commands EVAP canister purge valve open and EVAP vent valve closed. This allows engine vacuum to enter EVAP system. At a calibrated time, or vacuum level, PCM commands EVAP canister purge valve closed, sealing system, and monitors FTP sensor input to determine EVAP system vacuum level. DTC sets when system is unable to achieve calibrated vacuum level, or vacuum level decreases too rapidly.
The EVAP VALVE LOGIC table illustrates the relationship between the on and off states, and the open or closed states of the EVAP canister purge and vent valves.
| PCM Command | EVAP Purge Valve | EVAP Vent Valve |
|---|---|---|
| On | Open | Closed |
| Off | Closed | Open |
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.