An evaporative leak detection pump is part of the emission control system on your vehicle. It is concerned with evaporative (EVAP) emissions, preventing fuel vapors from escaping the fuel system. To prevent fuel evaporation, the fuel system traps and stores vapors coming from the fuel tank and routes them to the engine to be burned as part of combustion. Not only does this help to prevent fuel vapors from entering the atmosphere (something that has been shown to harm the environment and humans), but it also helps to increase fuel economy. The EVAP system also ensures that the fuel tank is properly vented so that pressure does not build up to dangerous levels.
According to federal law, EVAP systems must be able to perform periodic and automatic leak testing. If a leak is detected, the system must notify the driver. The evaporative leak detection pump is designed to apply pressure to the system in response to a command by the engine’s computer (engine control module or powertrain control module) and then measure for a drop in pressure signaling a leak. If a leak is present, the computer turns on the check engine light.
If the engine control module (by way of the leak detection pump) senses an evaporative leak in the fuel system, it will turn on the check engine light. But it will do the same if the leak detection pump fails. When a technician connects a diagnostic scan tool to read the stored trouble code(s), a failed leak detection pump might display codes such as P2401, P2407, or P2405. It is also likely that your vehicle will fail an emissions test. You might smell the odor of fuel coming from your vehicle, especially if the engine has been shut off, and you might notice a drop in fuel economy.
The evaporative leak detection pump is typically mounted on the evaporative canister assembly that stores captured fuel vapors before they are routed to the engine. The canister is located in a variety of places depending on the vehicle make and model, but it is frequently found near the fuel tank, in a rear wheel well, or near the trunk/cargo area of the vehicle. To replace the leak detection pump, a technician will take the following general steps:
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