What Does the Engine Code P0440 Mean?

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If your car is showing the P0440 engine code, there is a problem with your vehicle’s evaporative emission control system. This could be caused by a system leak or a fuel filler cap malfunction. 
Diagnostic trouble codes (DTCs) help you pinpoint a problem with your engine. You should never ignore the check engine light when it turns on. Instead, an OBD-II code reader can be used to identify and correct an engine issue.  
To help keep you and your car safe, car insurance comparison and insurance broker super app Jerry is giving you the breakdown on DTCs. In this article, we’ll discuss the P0440 engine code: what it means, how to fix it, and how much you can expect to pay for repairs. 
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What does the engine code P0440 mean?

Definition: Evaporative emission control system malfunction 
The P0440 engine code is signaling a problem with your vehicle’s evaporative emission control system (EVAP). The EVAP system is responsible for sealing the fuel system so that harmful fuel emissions cannot enter the environment. 

How much will it cost to fix?

The cost of a mechanic diagnosing the code is one hour of labor. Mechanic labor costs vary by region, but you can anticipate a charge of $75 to $150 an hour
If there is a leak in the EVAP system, the repair expense is determined by the location of the leak and what’s causing it. With these variables in mind, the cost to repair a leaky EVAP system is typically between $100 and $600.  

What can cause the P0440 engine code?

EVAP system issues are typically caused by one or more of the following:
  • Missing or loose fuel cap
  • Incorrect fuel filler cap being used
  • Fuel filler cap left open or unable to close
  • Foreign matter caught in the fuel filler cap
  • EVAP canister or fuel tank leaks
  • EVAP system hose leak
  • Leaking fuel tank

Common symptoms of the P0440 engine code

The main indicator that something is amiss with the EVAP system is your car’s check engine light or service engine soon warning light turning on. Other symptoms of EVAP system issues include:
  • The smell of fuel inside your car
  • Collapsed or leaky fuel tank

How serious is the P0440 engine code?

It depends. One of the most common causes of the P0440 code being triggered is a loose fuel tank filler cap, which can be fixed by either manually tightening the cap or replacing it if it’s damaged. 
If the code is being caused by a leak in the EVAP hose or canister (and you’re smelling fuel from inside the car), this needs to be addressed by a mechanic right away.  

Can I fix the P0440 engine code myself?

The key to fixing the P0440 engine code yourself is to diagnose the issue correctly

Start by examining your car’s fuel filler cap

Open the gas cap and examine the state of the fuel filler cap inside, looking for the following:
  • Is the fuel filler cap loose? Tighten the cap by hand until you hear it click. 
  • Is there something lodged inside it? Put on a rubber glove and gently try to remove it. 
  • Do you notice any cracks? A missing or damaged fuel filler cap can be replaced rather easily.
If the P0440 code was detected for any of these reasons, the check engine light should turn off after a couple of minutes of the fuel filler cap being properly reengaged. 

Diagnosing an EVAP system leak

Once you’ve ruled out all EVAP system issues related to the fuel filler cap, you must consider the probability of the P0440 code being triggered by a system leak. Unless you have significant experience working on cars, you’ll need to contact a mechanic to fix it. 

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