BD codes play a huge role in identifying vehicle’s problems. The P0442 code is the code used to identify a problem in the car’s Evaporation Emission Control system. It indicates a small leak has been detected in the EVAP system. In this article, we are going to look at what causes EVAP leaks and how to fix them.
An EVAP system is one of the largest systems found in vehicles. It is made up of many components located all through the car from the front to the back. Evaporative Emission Control System (EVAP) was introduced in vehicles as a means to preserve the environment.
Its main function is to prevent fuel vapor from escaping the fuel tank and fuel system into the atmosphere. EVAP systems rarely suffer from damage but when they do, finding the leak can be a difficult task to the large nature of the system, especially when the leak is small. The P0442 code is specifically for small leaks in the EVAP system.
Since the EVAP system is self-diagnostic, it usually does not need maintenance. They can still however develop faults and cause the engine light to turn on. When the engine light comes on, it prevents the car from passing an OBD II emission test.
The self-diagnostic monitor EVAP was introduced in 1996 and all vehicles since then have had it. It checks for gas vapor leaks and whether the gas caps are loose or missing. If it finds any of these, it sets a fault code and turns on the engine light.
The Components of the EVAP System
The EVAP system has four major components. They include:
The gas/fuel tank:
The gas tank is built with additional space so that when the gas expands, it does not leak over and cause an EVAP error code.
The fuel cap:
In old vehicles, the gas cap has a pressure relief valve. This is before OBD II was introduced. It is however sealed in newer vehicles (vehicles made from 1996 onwards). Always remember that when replacing the fuel cap, it should be the same as the original that came with the car.
The liquid-vapor separator:
This is a little separator that prevents gasoline from dripping into the vent line to the EVAP system canister. It is dangerous when gasoline goes directly to the canister. This is because the gasoline will cause the canister to lose its ability to store gas vapors.
It is located on the top of the gas tank or in some vehicles, on the overflow tank. The liquid-vapor separator rarely develops any issues. The most common issue is when the liquid becomes polluted with debris and rust that case an external leak. Different model cars have different liquid-vapor separators.
In such vehicles, a float and needle are placed inside the separator and when liquid enters, the float rises and pushes the needle to close the vent. Others use a foam-filled dome-shape material on top of the gas tank. Vapor passes through the foam but liquid is trapped by the foam.
If it happens that the liquid-separator is blocked by something, the fuel tank will lack proper circulation. The lack of circulation causes fuel starvation. Fuel starvation is when there is a wave of pressure when the gas cap is opened.
You should be able to blow into the vent line (into the fuel tank) if the system is clear. The blowing can sometimes clear blockages. If this does not work, remove the gas tank and diagnose it, or let a qualified mechanic do it for you.
EVAP canister:
The EVAP canister is a round or rectangular plastic mounted somewhere in the car, hidden from view. It may be located inside the hood or somewhere in the rear quarter ot the vehicle.
The EVAP canister is filled with charcoal (about a pound) that acts as sponge by absorbing gas vapors. The gas vapor is stowed until the car the car is driven. When the vehicle is being driven, the gas vapor is siphoned into the engine. The EVAP canister, like the liquid-vapor separator, is not prone to problems.
However, the most common problem is a faulty vent solenoid or purge control. You can test the solenoid by applying voltage directly to it and check whether the valve opens. The purge control can be tested by applying a vacuum to it using a pump. Observe the valve to see if it opens, if it does not open, there is a problem.
How to diagnose P0442 code?
To diagnose a P0442, you need the following tools: OBD II Scanner, a digital mutimeter and a smoke machine. Once you have these tools, follow the following steps to diagnose and repair the problem.
- Scan the car for other potential trouble codes. This is done to identify problems that should be fixed before the P0442 code. Problems with fuel injection and fuel pressure should always be fixed first while the P0442, P0440, P0446 are EVAP leaks and are after.
- Inspect the gas cap to make sure it is not loose
- Check the EVAP system pipes and hoses for leaks and cracks and make sure they are tightly connected. If they are, use the smoke machine to do a smoke test. This is done because P0442 code means there is a small leak that cannot be found or seen by the naked eye.
- Check the fuel tank for leaks
- Use the multimeter to test the charcoal canister vales. You should always disconnect the valves when testing.
Other OBD II Fault Codes
In 1996 when self-diagnostic EVAP systems were introduced, OBD II codes also came as a result. The OBD II system checks the gas system for gas leaks to ensure none of it is reaching the atmosphere. However, the EVAP monitor does two main things: ensure air does not flow from the EVAP canister to the engine and no leaks occur in the gas tank, canister and vent lines.
The OBD II fault codes include:
P0440….Evaporative Emission Control System Fault
P0441….Evaporative Emission Control System Incorrect Purge Flow
P0442….EVAP Emission Control System Leak Detected (small leak)
P0443….EVAP Emission Control System Purge Control Valve Circuit
P0444….EVAP Purge Control Valve Circuit Open
P0445….EVAP Purge Control Valve Circuit Shorted
P0446….Evaporative Emission Control System Vent Control Circuit
P0447….EVAP Emission Control System Vent Control Circuit Open
P0448….EVAP Emission Control System Vent Control Circuit Shorted
P0449….EVAP Emission Control System Vent Valve/Solenoid Circuit
P0450….Evaporative Emission Control System Pressure Sensor
P0451….EVAP Emission Control System Pressure Sensor
P0452….EVAP Emission Control System Pressure Sensor Low Input
P0453….EVAP Emission Control System Pressure Sensor High input
P0454….EVAP Emission Control System Pressure Sensor Intermittent
P0455….EVAP Emission Control System Leak Detected (gross leak)
P0456….EVAP Emission Control System Leak Detected (small leak)
P0457….EVAP Emission Control System Leak Detected (fuel cap)
P0440, 455 and 457 can be inspected by opening the fuel cap, inspecting it for any debris damage. Close it and ensure it’s tight by listening for a click. The error code should clear if the leak was in the cap. If the light remains on, there is probably a (larger) leak elsewhere in the system.
Conclusion
The cost of repair for P0442 is quite affordable. It is important to practice good vehicle maintenance habits to prevent damage to the EVAP system. Other than a slight odor and reduced fuel efficiency, it is difficult to identify a P0442 code. This is why regular maintenance is recommended.
