| Evaporative emission (EVAP) vent valve - valve stuck closed
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|EVAP vent valve
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Table of Contents
- What Does Code P2422 Mean?
- Where is the P2422 sensor located?
- What are the common causes of code P2422?
- Get Help with P2422
What Does Code P2422 Mean?
OBD II fault code P2422 is a generic code that is defined as “Evaporative emission (EVAP) vent valve – valve stuck closed”, and is set when the PCM (Powertrain Control Module) detects that the EVAP (Evaporative Emissions Control System) vent valve is stuck in the closed position. Note that depending on the application, code P2422 could mean that the valve is actually stuck in the closed position, or, that it cannot be commanded to open due to a failure or malfunction in its control system, or, that the vent valve cannot communicate its status (whether it is open or closed) to the PCM. Also, be aware that if code P2422 is present, other codes relating to the EVAP system are often also present.
The purpose of the EVAP system is to capture and contain harmful fuel vapors before they can escape into the atmosphere. On all applications, fuel vapors are contained within the EVAP system until the PCM determines that operating conditions are such that purging the contained fuel vapours into the inlet tract to be combusted will not affect engine operation negatively.
Although some design specifics vary from application to application, all EVAP systems consist of the fuel filler cap, the fuel tank, a charcoal-filled canister that temporarily stores fuel vapors, pressure and flow sensors, various hoses and vacuum lines, as well as purge and vent valves that are most commonly controlled with electrically operated solenoids. Note that on some applications, a dedicated air pump, hoses, and pressure sensors are used for leak detection purposes.
In a fully functional EVAP system, fuel vapours are collected and stored in a charcoal-filled canister that is connected to a normally closed vent valve to prevent fuel vapors from escaping into the atmosphere. Additionally, and assuming that the fuel filler cap is gas tight and that there are no leaks in the system, the purge valve through which fuel vapors are extracted into the engine is also normally closed, which means that the EVAP system is sealed off from the atmosphere. Under these conditions, the fuel vapor volume (and pressure) is allowed to increase until a predefined maximum threshold is reached.
NOTE: On some applications, this sealed-off condition also allows the PCM to run leak detection tests by pressurizing the EVAP system, while on other applications, the PCM will open the purge valve (while keeping the vent valve closed) for a set period of time to allow engine vacuum to create a vacuum in the system.
Thus, when the PCM determines that the collected fuel vapors need to be purged from the system, and that operating conditions are suitable, it will open both the purge and vent valves to allow engine vacuum to draw stored fuel vapors from the charcoal canister. However, to ensure proper evacuation of the charcoal canister, opening the vent valve allows ambient air at atmospheric pressure to help “push” stored fuel vapors from the charcoal canister. This process is known as a “purge cycle”, and both the vent and purge valves are closed by the PCM at the conclusion of each cycle until the fuel vapor pressure again approaches the maximum threshold.
From the above it should be obvious that the EVAP vent valve is a critical component in the EVAP system, and should the PCM detect that the vent valve has failed, in the sense that it is stuck in the closed position, it will set code P2422 as a result. Note that on some applications the PCM will also illuminate a warning light on the first failure, while on other applications several failure cycles need to occur before a warning light is illuminated.
Where is the P2422 sensor located?
The image above shows a simplified schematic of a typical EVAP system with the vent valve (circled in red) shown in relation to other major components of the system. Note however that although the EVAP vent valve is always connected to the charcoal canister and is sometimes incorporated into the canister, the actual location of the vent valve/canister assembly varies greatly between applications, and even between models in the same model range.
On some applications, the EVAP vent valve is reasonably easily accessible near the fuel tank when the vehicle is lifted off the ground, while on others, the fuel tank may have to be removed to gain access to the vent valve and charcoal canister. Therefore, it is important to refer to the manual for the affected application to locate and identify the vent valve correctly, since on some applications it is easy to confuse the EVAP vent valve with the EVAP purge valve.
What are the common causes of code P2422?
Some common causes of code P2422 could include the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors in the vent valve control circuit
- Defective vent valve
- Defective vent valve solenoid
- Failed or failing PCM. Note that this is a rare event, and the fault must therefore be sought elsewhere before any control module is replaced
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