What Does the OBD-II Engine Code P0442 Mean?

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If you see engine code P0442, you have a problem with the evaporative emission control system. This problem isn’t critical, but it will decrease your fuel economy. Take the car in for repairs as soon as possible to make sure there are no other underlying issues.  
Diagnostic trouble codes (DTCs) let you know what issues your car’s engine is having. If you have an OBD-II code reader, you’ll be able to identify the code at home and get an idea of the scope of the problem. 
Car insurance comparison and broker app Jerry has compiled the following guide with expert information to help you with DTCs. Here’s the rundown on the P0442 engine code so you know what’s wrong, how to deal with the issue, and how much it would cost to fix. 
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What does the engine code P0442 mean?

Definition: Evaporative emission control system leak detected—small leak
The P0442 engine code indicates a problem with your car’s evaporative emission control system, which is responsible for preventing gasoline vapors from escaping. 
These vapors are usually collected in a charcoal canister and burnt off by the engine.

How much will it cost to fix engine code P0442?

Running a diagnostic for the P0442 will cost around an hour of labor and run you between $75 and $150 per hour.
The cost of repairs can vary depending on what part(s) you need to replace. On the low end, a replacement gas cap will cost $20-$40, but on the high end, you may need to replace the charcoal canister for $200-$500.

What can cause the P0442 engine code?

The P0442 code indicates that the control module has detected a small leak in the Evaporative Emissions System (EVAP). This leak is most commonly due to a loose fuel tank filler cap.
The EVAP is responsible for keeping gasoline vapors contained so that they can be absorbed by the charcoal canister. When the car is turned off, the engine control module (ECM) carries out a leak test to ensure the EVAP system is working properly.
Other potential issues that could cause this engine code include: 
  • Missing or loose fuel cap 
  • Incorrect fuel filler cap in place 
  • Fuel filler cap will not close 
  • Something stuck in the fuel filler cap 
  • EVAP canister or fuel tank leaks 
  • EVAP system hose leaks 
  • Fuel tank leaks

Common symptoms of the P0442 engine code

You likely won’t notice anything when your EVAP system isn’t working aside from the check engine light turning on. Other potential signs to watch for include: 
  • Reduced fuel efficiency
  • Increased emissions
  • Gasoline smell

How serious is the P0442 engine code? 

The P0442 engine code is a minor problem and will not affect your car’s performance. However, it should be resolved before your next emissions test or you could risk failing the emissions inspection.

Can I fix the P0442 engine code myself?

In some cases, you can fix the P0442 engine code at home, but you should only carry out repairs if you can diagnose the issue correctly
Depending on the issue, you may have to do the following:
  • Replace the gas cap
  • Replace a faulty canister purge valve
  • Repair the fuel tank
If you’re not sure what repairs your car needs, you can cause serious damage to the engine. Bring your car to a professional to complete a thorough diagnostic inspection and repairs to stay on the safe side. 

Repairing the P0442 code

If you do decide to repair the P0442 code by yourself, you can follow these steps:
  • Identify what is causing the code to show up and follow the below steps as required.
  • Replacing the gas cap
  • Inspect the gas cap condition
  • Clean the gas tank and gas cap with WD-40 cleaner
  • Replace the gas cap with the correct model if it is damaged
  • Replacing the canister purge valve 
  • Inspect the canister purge valve next to the throttle body while the engine is running
  • Check the vacuum port for its functionality with your finger—the purge valve is stuck if you experience sucking
  • Replace the canister purge valve by removing the used purge valve and reinstalling a new one 

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