What the P0442 Code Means – Causes & Solutions

There are some faults that cause your engine check lights to come on that are simple to check and fix.

Other faults can take hours to find or diagnose. The P0442 code and the rest of the related EVAP codes fall into the latter category and can be a pain to solve.

What the P0442 Code Means

The P0442 code is triggered when the EVAP emission control system detects a small leak. The code refers to a problem somewhere in the system that prevents gasoline vapors from reaching the atmosphere. The fuel tank vent line vents to a charcoal filter from where the gas is burned by the engine.

The problem with small leaks is that they are incredibly difficult to locate, as they can be as small as a pinhole.

To locate the leak, specialist equipment is required along with an ultraviolet dye which makes finding the problem a little easier.

What the EVAP Emission Control System Is and What it Does

There are many different harmful chemicals in the fuel we use in our cars. At last count, there were more than 150 substances in our fuel, including toluene and benzene, which cause breathing problems, nausea, headaches, and dizziness.

Apart from being a leading cause of smog, gasoline evaporation can cause death in large enough quantities.

To combat the growing problems of gasoline vapor escaping into the air, environmental regulations were put in place during the 1970s and 1980s to reduce the amount of vapor that cars and other vehicles were permitted to release into the atmosphere.

Car manufacturers installed EVAP systems that stored and then disposed of fuel vapors that escaped from fuel tanks and engines.

How the EVAP System Works

A small canister filled with charcoal is used to capture the gasses from where they are transferred to the engine combustion chambers.

The process makes use of valves and hoses as well as fuel line vents and a sealed fuel cap.

Each of these components suffers from wear and tear, but it is unusual for the system to break down. Unfortunately, rubber seals do corrode and valves, pipes, and hoses are prone to mechanical failure.

Less sophisticated EVAP systems are controlled mechanically, while the latest technology is utilized on newer vehicles and relies on sensors and the engine’s computer to send signals to the valves that release the stored gases.

What Can Go Wrong with the EVAP System

Gasoline has the propensity to change from a liquid to a gas very quickly. This process accelerates as the temperature increases. With as much as 20% of all hydrocarbon discharge coming from fuel evaporation, this is where the EVAP systems focus.

With the lack of maintenance, faults are often only picked up once the check engine light comes on. And when it does, the computer can suddenly decide that the engine is unable to run, leaving you stranded.

The most common faults occur with the purge valve, followed by leaks in the vent and vacuum hoses.

The easiest faults to rectify are ones that are related to the gas cap. If your gas cap becomes loose, doesn’t seal properly or if the cap is missing altogether, then replacing it will usually solve the problem quickly and inexpensively.

The P0440 code is often triggered by a problem with the gas cap and is described in the diagnostic manual as a large leak.

If the problem is related to the purge valve, then you can expect a code from P0443 to P0449 to show up.

Fixing the P0442 Code Fault

While the P0442 code is not critical, it can increase your fuel consumption and will result in your vehicle failing an OBD-II emissions test.

Fixing the problem depends on what is causing the error, with a diagnostic test and replacement gas cap setting you back between $100 and $200. If the gas canister requires replacement, you could be in for a repair bill of over $500.

Replacing the gas cap yourself or checking and replacing the gas canister and purge valve are within the capabilities of a DIY mechanic, but further than that, you’ll need specialist equipment to find very small leaks.

Finding Small Leaks with a Smoke Tester

To assist in finding the small leaks that may trigger the P0442 code, technicians will often use a smoke machine. Using a mineral-oil vapor, smoke is introduced into the EVAP system under pressure to reveal where the gas may be escaping.

To make the task easier, an ultraviolet dye is added to the mineral-oil base so that it shows up under a black light. This is not normally a task to be undertaken at home, so you’ll have to take your vehicle to a repair shop for the diagnosis and repair.

The Liquid-Vapor Separator

Another component that may cause you trouble is the liquid-vapor separator.

The separator is located above the fuel tank and its job is to ensure that no liquid fuel finds its way into the charcoal canister.

If liquid fuel enters the canister, it will fill up very quickly and not be able to contain the vapors that it is designed for. If the separator becomes clogged due to rust or scale, it can cause the system to fail.

The separator can also not work properly if the main vent line is blocked or narrowed due to rust or physical damage caused by vibration or metal fatigue.

Problems of this nature are very difficult to diagnose and can sometimes even require the removal of the fuel tank. This is both dangerous and time-consuming, so proper diagnosis by a technician is recommended.

Frequently Asked Questions on What the P0442 Code Means

Conclusion On What the P0442 Code Means

Any time you are hit by the smell of gasoline inside your vehicle and the engine check light comes on, you may experience a problem with your EVAP system.

While getting an EVAP error code is not always a serious problem, it will affect your fuel consumption and possibly prevent you from passing your next vehicle inspection.

The EVAP system is relatively maintenance-free, but when things go wrong, you can likely fix them yourself without too much trouble.