The DTC P0442 code tells you there’s a leak somewhere in your evaporative emission control system. While it gives you some data about the size of the leak, it doesn’t identify a specific location. This is what can make this particular trouble code somewhat tricky to diagnose.
Even though P0442 doesn’t indicate a serious problem, you’ll want to fix it before your next inspection. Read on below to learn the best way to diagnose and repair this sometimes troublesome trouble code.
P0442 Code Definition
P0442 Code Definition (Generic): Evaporative Emission Control System Leak Detected (small leak)
P0442 Dodge: EVAP System Leak Detected (small leak)
P0442 Code Ford: (EVAP) system leak detected (small leak .04-inch)
P0442 Subaru: EVAP Control System Leak – Detected (small Leak)
What Does P0442 Mean?
The P0442 OBD2 code is generally related to your evaporative emission control (EVAP) system. This system helps prevent smog-forming compounds from entering your exhaust. The vapors from the fuel tank go through a chamber that contains charcoal pellets. These pellets absorb the harmful compounds, sending cleaner carbon dioxide along into your engine intake manifold.
There are valves on either side of the charcoal canister. The one that lets fuel vapors in is called the vent control valve. The one that lets carbon dioxide out is called the purge valve. Normally, both these valves stay open when your engine’s running. The ECM tests the valves periodically, though, closing them to form a vacuum. If pressure isn’t maintained during one of these tests, the P0442 code activates.
You’ll see different OBD2 trouble codes depending on the size of the leak in your EVAP system. The P0442 code triggers for a medium-sized leak, measuring between .02” and .04” in diameter. Leaks this small aren’t likely to cause serious problems, but they can be a bit tricky to locate.
What Are The Symptoms Of The P0442 Code?
It’s unlikely you’ll notice any problems when you drive your car. The main symptoms associated with the P0442 trouble code are:
- Activation of the check engine light
- Reduced fuel efficiency
- Slight smell of fuel while driving
What Are The Causes Of P0442?
- Gas cap is loose or damaged (most common)
- Leaking fuel tank
- Leaks or damage in the EVAP hoses
- Purge valve is faulty
- Vent control valve is faulty
- Charcoal canister is clogged, damaged, or leaking
- Leak detection pump is faulty
How Serious Is The P0442 Code?
There is a minimal risk of damage to your vehicle with the P0442 OBD2 code. The severity level of this code is low. You will want to fix the problem before your next inspection, but you can drive your car safely until you have a chance to make the repair.
How To Diagnose The P0442 Code
Many manufacturers put out bulletins related to EVAP trouble codes. Search for any technical service bulletins that have recently been released for your vehicle before starting your diagnosis. The repair process for P0442 tends to be more vehicle-specific than those for other trouble codes.
Tools you’ll need:
- Scan your vehicle for other trouble codes. If any come up related to the fuel system, especially fuel pressure issues, fix those first. Codes P0440, P0441, or P0446 in conjunction with P0442 likely indicates an EVAP leak.
- Read the freeze frame data for your EVAP system to see what conditions were present when the code occurred.
- Inspect the gas cap for damage and make sure it’s tightly installed.
- Check the hoses of the EVAP system for leaks, cracks, or other damage. Make sure they’re all tightly connected. Because the leaks indicated by P0442 are so small, a smoke test is recommended. You can conduct one by connecting a smoke machine on visible vapor mode to your EVAP system.
- Check both the fuel tank and the charcoal canister for leaks or build-up.
- Use a digital multimeter to test both the valves on the charcoal canister. Disconnect the valve from your system then test it with the multimeter. If it’s not receiving power, check the wiring around the valve.
Common Mistakes To Avoid While Diagnosing The P0442 Code
Don’t ignore other codes that appear with P0442. It’s likely to see other trouble codes related to the EVAP system at the same time, such as P0440, P0441, P0443-P0449, P0452, P0453, P0455, and P0456. Take note of these, as they can help you to diagnose what triggered P0442.
You also shouldn’t assume that the gas cap is causing P0442, even though that is the most likely source of the issue. Perform a full diagnosis to check for other problems before you assume the gas cap is the culprit.
What Should You Do To Fix The Code P0442?
After every step of the repairs, clear the codes using an OBD2 scan tool then check your car again. The most common fixes are fortunately also the easiest and most affordable to repair.
- Take any repair steps recommended in any technical service bulletins related to the P0442 code for your vehicle.
- Replace any damaged hoses found during step 4 of the diagnosis. If the P0442 code recurs, conduct a second smoke test to make sure you’ve fixed all the leaks.
- Replace your gas cap, even if you don’t see any damage. Make sure you replace it with an OEM component rather than an after-market product. Mis-fitting gas caps can be one cause of the P0442 trouble code.
- Remove the charcoal canister and inspect the passages and lines around it for build-up or damage. Clean any deposits with throttle body cleaner.
- Replace any damaged wires you see around the valves of the EVAP system, then test the valves again with a multimeter. If they still fail, replace the vent control valve or purge valve as necessary.
Tips To Avoid P0442 In The Future
Always make sure you tightly replace your gas cap after you fill your tank. If you lose your gas cap, don’t just replace it with the first one you find. Spend the extra few dollars to get an OEM part. If the gas cap doesn’t fit correctly, you’ll likely continue to get EVAP leak trouble codes.
Safeguarding your engine with an anti-rust agent can help prevent corrosion that leads to leaks. You can buy products to do this at home or ask your mechanic to do it during your next oil change.