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Code P0440

Symptoms

• Check Engine Light is on

• Slight decrease in fuel efficiency

• Fuel smell from the vehicle

Common Causes

• Loose or faulty gas cap

• Cracked or damaged EVAP hoses

• Faulty purge or vent valve

Glossary

EVAP: Evaporative Emission Control System

ECM: Engine Control Module

Related Codes

• P0441

• P0442

Official description

Evaporative Emission Control System Malfunction

Laymans terms

This code means there's a problem with the car's system that keeps gasoline fumes from escaping. It's like if the lid on a soda bottle wasn't screwed on tight, and the bubbles could get out.

Explanation

The P0440 code indicates that there is a malfunction in the Evaporative Emission Control (EVAP) System, which is designed to capture and store fuel vapors from the fuel tank and prevent them from escaping into the atmosphere.

Technical description

The EVAP system captures fuel vapors from the fuel tank and stores them in a charcoal canister. The vapors are then purged into the engine to be burned. A P0440 code is triggered when the Engine Control Module (ECM) detects a leak or a problem in the EVAP system, which could be due to a faulty gas cap, a leak in the hoses, or a malfunctioning component.

Diagnosis steps

• Check the gas cap for proper installation and condition

• Inspect EVAP system hoses for cracks or damage

• Test the purge and vent valves for proper operation

Repair procedures

• Tighten or replace the gas cap

• Replace damaged EVAP hoses

• Replace faulty purge or vent valve

Tools required

• OBD-II scanner

• Vacuum pump

• Smoke machine

Estimated repair cost

$50 - $200

Difficulty level

Moderate

Commonly affected vehicles

• Toyota Camry

• Honda Accord

• Ford F-150

Preventive measures

• Ensure gas cap is tightly secured after refueling

• Regularly inspect EVAP system components

• Use high-quality fuel caps

Error code type

Emission Control System Issue

User experience recommendations

• Check the gas cap first; it's an easy fix if that's the problem.

• Avoid topping off the fuel tank to prevent EVAP issues.

Warranty information

EVAP system components may be covered under the vehicle's emissions warranty.

Historical data

P0440 is a common code that has been reported frequently since the introduction of OBD-II systems in the mid-1990s.

Urgency level

Low – This issue does not affect immediate drivability but should be addressed to maintain emissions compliance.

Legal and safety notice

Driving with an EVAP system malfunction may not be legally compliant with emissions standards in some areas.

Testing conditions

• Engine at operating temperature

• Fuel tank between 1/4 and 3/4 full

Component location

The EVAP system components are typically located near the fuel tank and engine bay.

FAQs

Q: Can I drive with a P0440 code?
A: Yes, but it's best to fix it soon to ensure your car remains emissions compliant.

Q: Will a P0440 code cause my car to fail emissions tests?
A: Yes, a P0440 code will likely cause your car to fail an emissions test.

Last updated: Oct 28, 2025 • Source: internal database
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