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P0440 is a diagnostic trouble code (DTC) for "Evaporative Emission Control System Malfunction". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
Evaporative Emission Control System Malfunction
P0440 is an OBD-II generic code that the engine control module (ECM) has detected a leak in the fuel tank vapor system or a vapor pressure sensor has malfunctioned.
The ECM has closed off all of the fuel tank vapor lines and monitors the vapor pressure and sees a pressure drop more than is allowed within the test parameters of the ECM.
The cause of code P0440 can be a loose gas cap which is the most common reason for the code.
Code P0440 is also set if any component in the fuel vapor system is leaking like a gas cap vent, vent valve, carbon canister, fuel filler neck, or any of the many fuel vapor recovery components.
The fuel vapor pressure sensor is faulty causing an incorrect reading input to the ECM.
The Check Engine Light will be illuminated and the code is set in ECM memory.
You may notice a fuel vapor odor in or around the vehicle if vapor leak is large enough,
Scans codes and documents the code in the ECM. Views the freeze frame data to see when fault happened.
Inspects the entire fuel system to include the fuel lines and vapor lines from the front to the rear of the vehicle for any signs of fuel or vapors leaking.
Checks to make sure the fuel cap is not loose as this is the most common problem.
Performs a smoke leakage test on the fuel vapor system to try and locate the cause of the vapor leak using the test vapor port.
If no leaks are present, then follow the manufacturer pinpoint test for detailed checking of the vapor sensor and system for this code since these systems can be very different between manufacturers.
Assuming the gas cap is leaking without doing a thorough diagnostics of the complete system.
Failing to check with the customer to see if the gas cap was left loose recently.
Code P0440 causes the Check Engine Light to go on and this alone will cause a failed emission test.
The code means the fuel vapor system has a vapor leak somewhere in the system and vapors can be very flammable and dangerous to breath the vapors.
The loss of vapors in the system only means the engine did not use them and this may cause a loss of fuel mileage.
Tightening or resetting the fuel cap.
Replacing a leaking fuel cap that has a bad seal or vent in the cap.
Repairing or replacing leaking vapor system components like a vapor control valve or carbon canister.
Code P0440 is one of the most common codes that causes the Check Engine Light to come on in vehicles today. The most common cause for this is the fuel cap being accidently left off or not tightened securely after getting fuel.
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