P0442: Evaporative Emission Control System Leak Detected (Small Leak)

Your OBD-II diagnostic scanner may register a P0442 EVAP leak detected diagnostic trouble code. If so, you are probably wondering, how do I fix trouble code P0442?

Your vehicle's powertrain control module monitors the Evaporative Emission Control System for leaks and other problems. If you see a P0442 DTC, you know there is a fuel vapor leak somewhere in the EVAP system. The small leak code tells you that the leak is probably minor.

Possible Causes of P0442

If your OBD-II diagnostic scanner registers a P0442 DTC, you must find and repair an EVAP system leak. Here are some common reasons you may see this code:

  • A loose or incorrectly affixed gas cap
  • A gas cap that does not meet vehicle manufacturer standards
  • A tiny crack or hole in a fuel vapor hose or tube 
  • A different type of leak somewhere else in the EVAP system
  • A faulty vent or purge valve
  • A bad vent seal
  • An unreliable leak detection pump 

Potential Simple Resolutions

Now that you understand the possible causes of this DTC, you need to know how to fix the problem. Fortunately, you may be able to resolve the issue without much effort.

The simplest solution is to remove and reattach the gas cap. Once you do, clear the code on the OBD-II scanner and drive for a few days. If the code does not return, your gas cap probably was the culprit.

Of course, there is a chance your gas cap either has worn out or is not compatible with your EVAP system. To troubleshoot this, replace the cap using an OEM component.

If tightening or replacing your vehicle’s fuel cap does not resolve the code, visually inspect your EVAP system for tears, holes, or cracks in its tubes and hoses. If you see any, replace the damaged component.

Potential Advanced Resolutions

As you may suspect, sometimes tinkering with the fuel cap and visually inspecting the EVAP system may not resolve your OBD-II scanner error code P0442 problem. If that is the case, use an advanced scan tool to perform an EVAP leak test. The scan tool locates leaks that are either hidden or imperceptible to the naked eye.

Alternatively, check the functionality of the EVAP purge valve and solenoid. If either of these are defective, replacing the bad part with an OEM component may fix the problem. If that fails, you may need to perform a smoke test to find the EVAP system leak.

Whether a simple or advanced approach takes care of your DTC, finding the source of the code is essential both for ensuring your vehicle’s emissions stay within normal parameters and turning off your check engine light.

Your Vehicle’s EVAP System

Modern vehicles have a way to minimize emissions. To do so, a purge control valve must open. Then, an intake vacuum sucks fuel vapors into the engine where they burn off, decreasing overall emissions.

What does the code P0442 mean? As with any system of hoses, valves, and vacuums, leaks are the enemy. If your EVAP system springs one, fuel vapors may seep out before your vehicle’s engine can incinerate them. Because noticing a leak without computer assistance can be challenging, the OBD-II scanner alerts you to a leak by generating a P0442 DTC. Again, this code tells you your EVAP leak is small.

Warning Signs

Unlike some other vehicle problems, a leaky EVAP system may not cause your vehicle to run poorly. Instead, you are likely only to see an illuminated check engine light. Depending on the location of the leak and its size, though, you may smell fuel or exhaust fumes. Still, using an OBD-II diagnostic scanner to read your vehicle’s codes is the best way to uncover a leak in the EVAP system.

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