#OBD Codes
P0442 – Evaporative emission control system small leak detected
Technical definition
EVAP emission control system (small leak). Leak detected.
What does P0442 mean?
Trouble code P0442 indicates a small (about 0.5-1.0 mm in diameter) fuel vapor leak in the evaporative emission control system (also known as EVAP). This system reduces air pollution by preventing fuel vapors from escaping from the gas tank into the atmosphere. It traps vapors in a charcoal canister until the engine can burn them.
The engine control unit (ECU) performs periodic tests to ensure the proper EVAP system operation. If the ECU detects an EVAP system leak, it triggers a trouble code and turns on the check engine light.
The P0442 code usually indicates a minor problem, such as a loose gas cap, damaged vapor lines, a faulty canister purge valve, or a crack in the fuel tank.
Diagnostic trouble code P0442 often appears with other EVAP-related codes. It's important to pay attention to them because these codes can help pinpoint the root cause of the problem. For more information on how to interpret related codes, see the "Scan for other codes" section below.
How serious is P0442?
Trouble code P0442 isn't critical and won't affect your vehicle's performance. However, it increases air pollution by releasing fuel vapors into the atmosphere. Luckily, fixing it is relatively inexpensive.
Can I still drive with P0442?
Yes, you can still drive with a P0442 fault code, but it's wise to address the issue soon. While an EVAP leak won't cause immediate damage, ignoring it can lead to other issues. For instance, a persistent check engine light may mask a new engine problem.
In addition, fuel vapors harm the environment and your health. Prolonged exposure to these vapors can cause headaches, breathing difficulties, intoxication, and other respiratory problems.
Symptoms of P0442
If your car has a P0442 code, you are unlikely to experience any changes in performance, but some symptoms can arise. Besides the check engine light, the most common sign is a fuel smell near the gas cap or inside your car.
If the leak gets worse over time, you may notice an even stronger smell and a slight decrease in fuel economy.
Common causes of P0442
- Loose or broken fuel cap: This problem is the most common and the easiest to fix. Fuel vapors can escape and trigger the code if the cap doesn't seal properly.
- Cracked or damaged EVAP hoses: Over time, hoses can become very brittle and crack.
- Faulty EVAP canister purge valve or canister vent valve: If these valves don't seal properly, they can also cause vapor leaks.
- Cracked fuel tank: While less common, cracks can occur due to wear and tear.
- Malfunctioning leak detection pump: A faulty pump can incorrectly detect leaks and trigger the P0442 code.
How to troubleshoot P0442
Use these tips to diagnose and fix a P0442 code accurately:
Scan for other codes
Use an OBD scan tool to check for other related trouble codes, which may provide additional clues to the underlying problem. These include:
P0440 and P0456: Indicate issues with the EVAP system similar to P0442 but might point to smaller leaks or general malfunctions
P0441: Points to problems with the purge flow, which could help identify if the issue is related to the purge valve or flow path
P0443: Suggests an electrical issue with the purge control valve circuit
P0446: Indicates a problem with the vent control circuit, which can help focus on the vent valve and associated components
P0450-P0454: These specifically relate to the EVAP pressure sensor. Issues with this sensor can affect leak detection and overall system performance.
P0457: Indicates that the gas cap is loose or damaged
Clear the code and test drive
Use the OBD2 reader to clear the trouble codes. Then drive your car for a day.
After the drive, scan the car to see if the same problem occurs again. If it doesn't, it may just be a one-time occurrence. But if the code reappears, it's an ongoing failure that requires further investigation to fix it.
Check the gas cap and seals
Make sure the gas cap is tight and undamaged. Check the condition of the rubber O-ring and replace it if necessary. If you notice any dirt or debris on the gas cap or seal, clean it using WD-40.
Use a smoke machine
A smoke test is an effective way to locate EVAP leaks by filling the system with smoke. The smoke visibly escapes from any cracks, holes, or loose connections, so it's easier to identify the exact location of the issue.
Inspect EVAP hoses
Visually check for cracks, holes, or disconnected hoses. Replace any damaged ones.
Examine the fuel tank
Look for signs of damage or leaks in the fuel tank. If necessary, repair or replace the tank. A cracked fuel tank can leak fuel vapor and cause fire.
Check the leak detection pump
Ensure that the EVAP leak detection pump is working properly. If it's defective, it might incorrectly detect a leak. Replace the pump if necessary so you can detect leaks accurately.
FAQ
How much does it cost to fix P0442?
Fixing a P0442 code is relatively inexpensive, from just a few dollars for a new gas cap O-ring. In rarer cases, repairs can cost up to a few hundred dollars for a new fuel tank and labor.
What are the risks of ignoring the P0442 code for a long period?
If you ignore the P0442 code, you might fail a vehicle inspection and get fined.
Over time, a small EVAP leak can become larger, and you will smell a stronger fuel odor outside and inside your vehicle.
Disclaimer: Advice, how-to guides, and car care tips on our blog are intended as helpful resources for general maintenance and repairs. While we strive for accuracy, the information is provided to the best of our knowledge and should be used at your own discretion and risk.
Always refer to your vehicle's owner's manual or consult a certified mechanic for specific repair details and safety procedures.
Always refer to your vehicle's owner's manual or consult a certified mechanic for specific repair details and safety procedures.