The P0440 code - Definition, Symptoms and Causes. (& How to Fix It).

If your engine control module recognizes an error with the EVAP systems, a P0440 message will appear.

Sometimes, this trouble code can be less severe than you might think. This article will help you get rid of this trouble code.

Definition of P0440

Evaporative Emission Control – System Malfunction

What is the meaning of P0440?

If the P0440 is displayed, it means there's a problem with the EVAP emissions system.

The EVAP system, which is a sealed gas vapor device that extracts fuel vapors from the gasoline tank and combusts these through the engine rather than releasing them to the atmosphere, is a gas vapor system.

P0440 Symptoms

Other than the Check engine lamp on your dashboard, you won't likely experience any other symptoms. You may notice a mild increase in fuel consumption and gasoline smell, but this is rare.

• Smells of gasoline
• Verify Engine Light
• A slight decrease in fuel use

What is the severity of the P0440 code?

Very Low – Your car engine won’t experience any further damage from the P0440 code.

The engine may run slightly less in rare cases, but this will not affect the performance.

The P0440 code: Causes

The most common cause of the P0440 code is that you didn’t shut off your car at the gas station and let it run without the fuel cap tightened. Also, problems with the EVAP-purge control valve may be a problem.

• The fuel cap is not required for your vehicle to run at the station.
• Gas cap faulty
• Faulty EVAP Purge Control Valve
• Fuel tank damaged
• Canister damaged
• EVAP Pipes that are clogged or leaking

How can you fix P0440?

• Tighten the gas cap & remove trouble codes
• Seal the gas cap by replacing or replacing it
• Change the EVAP purge valve
• Wires must be connected to EVAP purge controller valve
• Replace fuel tank
• Canisters need to be replaced
• Repair damaged EVAP lines/pipes

Common Diagnostis mistakes

The most common error with P0440 codes is to try too many advanced diagnostics. There is a high chance that there is no problem with the EVAP system – someone maybe just forgot to shut off the car engine while refueling the car or forgot to tighten the fuel cap properly after refueling.

The trouble code for this code is very similar to P0442.

Diagnostic Tools

How do you diagnose the P0440 code?

1. Check for trouble codes by connecting a Diagnostic Scanner. While refueling, make sure that the problem code isn't accidentally saved.
2. Verify that the gas cap and sealing are tightened correctly.
3. The EVAP purge solenoid should be checked. Ensure the line is sealed when it is closed, and make sure it’s working by testing it with 12 volts and ground.
4. You should check if your ECU is sending any signals to the EVAP Purge solenoid. You can find a detailed guide on how to do this here: P0445.
5. You should pressurize the line from the tank to the gas pipe. If there's a leak you can use an EVAP smoking machine.
6. If the system is sealed and the purge control solenoid works – Remove the trouble codes and let the customer try the car for a couple of days.

Other Trouble Codes