EVAP leaks are painful. Small ones, even more so. This is because they cause the check engine light to almost be permanently illuminated with this trouble code, even though there is nothing seriously wrong with your vehicle.
Of course, the system is important for mitigating the emissions of vehicles when they are not being used. Luckily, the P0442 code doesn’t affect vehicle performance in any meaningful way, so that’s one less headache to worry about.
This guide will give take you through all the important information about this trouble code. You’ll find the causes, symptoms, diagnostic techniques, and anything else you might need to know about this trouble code.
What is the P0442 Code, and What Does It Mean?
The P0442 code is the trouble code for the “small EVAP system leak.” At engine start, your ECU runs a test for large and small holes in the evaporative emissions system. It does this by pressurizing the system and then looking for any drops in vacuum pressure. The tests are often so sensitive that even holes smaller than half an inch are registered.
Of course, this code means that fuel vapors are leaking through a small hole in the EVAP system.
How serious is a small EVAP leak?
Your EVAP system is an auxiliary system, not essential to the core functions of the vehicle. It’s not as serious as O2 sensor failure, or other codes. However, because it is there to improve the emissions of your vehicle, you might fail an emissions test if you have a P0442 code.
So, you can still drive your vehicle but watch out for your yearly emissions test if you’re in a state that mandates it.
What Causes the P0442 Code?
P0442 codes are notoriously difficult to clear. Luckily, the causes are relegated to the EVAP system, which helps narrow down your search. The most common causes are:
- EVAP vent solenoid failure
- Failed canister purge valve
- Cracked gas cap seal
- Small vapor line hole
- Wiring harness failure
EVAP Vent Solenoid Failure
The vent solenoid maintains optimal vacuum pressure in the EVAP system by releasing extra air when needed. Any failure in the internal seals and O rings will cause the P0442 code. Additionally, because the solenoid is electronically controlled, a wiring fault or corrosion can cause the solenoid to be stuck open.
Failed Canister Purge Valve
In a similar manner to the vent solenoid, the canister purge valve releases fuel vapor collected in the carbon canister, back into the engine when the vehicle starts. It can also fail in the same way, cracked seals can cause air to leak and the P0442 code.
Cracked Gas Cap Seal
This is a common cause of EVAP codes. With the P0442 code, cracked gas cap seals can cause small amounts of vapor to escape and trigger the code. It’s rare that the gas cap is missing rather than the seal being cracked.
Small Vapor Line Hole
The vapor lines carry fuel vapor that leaks from the fuel tank into the carbon canister, this prevents excess emissions when the car is not operating. Of course, holes can cause these vapors to leak from the EVAP system and cause the trouble code.
These are common because EVAP lines are usually not solid metal but are either rubber or plastic hoses. Areas where there are fittings bends, or lots of movement during driving, are prone to small holes.
Wiring Harness Failure
Both the canister purge valve and the vent solenoid are electronically opened and closed by the ECU. If the voltage signal between the ECU and either solenoid is disrupted, this will cause them to malfunction. Although these solenoids do have specific trouble codes for when they fail, if the solenoids are stuck open, it can cause a vacuum leak.
What Are the Common Symptoms of P0442 Fault Code?
The EVAP system does not affect drivability, this makes issues difficult to detect with normal intuition or knowledge. However, there are some telltale signs that you can use to detect a P0442. The three most common ones are:
- Check engine light
- Gasoline Smell
- Poorer Gas Mileage
Check Engine Light
Your check engine light is like the bat signal, telling you when there is an issue with your vehicle. More serious issues have their light and will cause the CEL to flash. The P0442 will not do this.
If you have a digital dash, look out for any messages related to the EVAP system or “Check Emissions System.”
Gasoline Smell
The function of the EVAP system means that when there are holes, you will smell gasoline from the vapors. It might not be enough to diagnose the problem, but if it is coming from the driver’s side, it is likely the EVAP system that is at fault.
Poorer Gas Mileage
This symptom might be difficult to notice or link to the P0442. Many issues can cause poorer gas mileage and even if the EVAP system is causing it, it will only be a slight change in gas mileage. However, if you combine it with the smell of gas vapors, it can be a symptom that you can go off of.
How to Diagnose and Fix the Cause of P0442 Code
Diagnosing the P0442 code can be intimidating. Taking it step by step is the best way to make the correct diagnosis and fix it. First thing first — inspect the fuel tank cap. A failed fuel tank cap is one of the most common causes of EVAP codes. Check out our selection of fuel tank caps for a quality replacement option.
OBD-II Reader
First, you need a tool to read the trouble codes from the ECU. This is an OBD-II scan tool. Once you have yours ready, plug it into the connection port. Scan for trouble codes, look for the P0442, and any additional trouble codes that can help you track down the issue.
Although this will not help you find the location of the leak, it is an important diagnostic step because you now know for certain the EVAP system is at fault.
Visual Inspection
Before you disassemble your EVAP system, it’s vital that you visually inspect for damage. The vapor lines are the easiest component to access. Check for any visible cracks or holes and move the lines from side to side to ensure that the fittings are not loose. Of course, this doesn’t rule out tiny holes in the vapor lines just yet.
Check your canister purge valve and vent solenoid for damage. Any corrosion, external dents, or burn marks mean that this part is likely the source of your trouble code.
Solenoid Test
First, you’ll check for resistance coming from each solenoid using a multimeter. Take the red probe and black probes and contact the solenoid terminal. Make sure your multimeter is set to OHMS. You should get around 14 – 30 Ohms.
Testing for continuity is also a great way to tell whether the sensor is opening or closing. Disconnect the solenoid from the EVAP system. Set your multimeter to continuity and contact each terminal with your multimeter probes. If it shows “OL”, it is malfunctioning.
Leak Test
Testing for leaks is the final conclusive test. The best way to conduct this is by using a smoke machine. Any holes will then emit colored smoke to guide you to where the leaks are.
Disconnect your EVAP hose that links to the engine. It should come straight from the canister purge valve. Connect your smoke machine to the EVAP system, via the disconnected hose. Run your smoke machine and check for any smoke leaking from the EVAP system or fuel cap.
If you don’t have access to a smoke machine, you can use water with dish soap and a spray bottle. With this method, any leaks will cause the liquid to bubble, so look out for that.
Does P0442 Clear Itself?
No, this code will not clear itself. Although every vehicle conducts a self-test for EVAP leaks when it starts, clearing the P0442 code is difficult. Finding every small leak in the system and fixing it is a tedious task. You want to have your OBD-II scanner on hand to clear the codes and check if they appear again to tell if there are other leaks.
Is It OK to Drive with P0442?
You can drive with a P0442. There’s almost no actual effect on your vehicle other than a tiny loss in gas mileage. If you have an emissions test coming up, you should get it fixed.
Fix Your EVAP Code with Quality Parts
At this point, you’ve found the EVAP leak, and you know you need to replace some components. The DIY knowledge to do this is one thing. As a car enthusiast, you already have that. You just need a reliable supplier for the parts that you need.
Our website, Newparts.com, is the destination to meet all your auto parts needs. Just select your vehicle from the dropdown list and search for the parts that you need. A tailored list for your vehicle will be right there for you.
