P0442: Evaporative Emission Control System Leak Detected

Modern vehicles have internal computers that not only control the overall performance of your car, truck or SUV, but also alert you to a problem by generating trouble codes. Of course, if your vehicle’s computer produces one, you need to know what your trouble code means to determine why your check engine light is on.

Decode Your Check Engine Light

This article addresses a common code: evaporative emission system leak detected. Before exploring the code definition and how to fix it, you should understand two important concepts.

  • The on-board computer diagnostic system is the integrated tool that monitors many of your vehicle’s essential systems. The OBD may alert you to problems with your vehicle’s engine, airbags, antilock brakes and other components. Since 1996, vehicles have an OBD-II diagnostic system. If your vehicle has this system, you need an OBD-II diagnostic scanner to communicate with its OBD system.
  • The diagnostic trouble code is the code your OBD generates to tell you something is wrong. The DTC allows you to home in on the system that is not functioning properly. For example, if your vehicle’s OBD detects a leak in the evaporative emission system, you may see a P0442 code. On most vehicles nowadays, there are hundreds of possible DTCs a car can generate.

The EVAP leak detected DTC is a powertrain code that many different makes of vehicles are capable of generating. That is, you may see this code on an OBD-II system for your BMW, Chevrolet, Chrysler, Dodge, Ford, GMC, Jeep, Subaru, Toyota or another type of vehicle. Additionally, while this DTC is not specific to a certain make or model of vehicle, the steps required to remedy it likely depend on the type of car, truck or SUV you drive.

The Code

If your OBD-II diagnostic scanner communicates an evaporative emission system leak detected code, you must understand what the code means. While this DTC is generic, it tells you a considerable amount about your vehicle’s evaporative emissions system. Again, this code may show up as P0442.

Your car’s power control module monitors the EVAP system for leaks and other problems. If you see an EVAP leak code, you know there is likely a fuel vapor leak somewhere in the system. The small leak code tells you that the leak in your EVAP system is minor. Still, if you do not want to fail an emissions test or look at an illuminated check engine light, you must find and fix the leak.

Your Vehicle’s EVAP System

As you likely know, modern vehicles have a way to minimize emissions. Yours probably has hoses that direct fuel vapors into a charcoal canister. When the canister becomes full and your vehicle’s engine engages, a purge control valve opens. The purged fuel vapors enter the engine where they burn off, decreasing overall emissions.

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 effectively incinerate them. Because noticing a leak without computer assistance can be challenging, the OBD alerts you to a leak by generating an EVAP leak detected DTC.

Warning Signs

Unlike some other vehicle problems, a leaky EVAP system may not reveal itself by causing 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 fumes. That said, using an OBD-II diagnostic scanner to read your vehicle’s codes is the best way to diagnose problems with the EVAP system.

Possible Reasons

If your OBD-II diagnostic scanner registers a P0442 EVAP leak detected DTC, you know there is likely a leak in the EVAP system. There are a few possible reasons this code may appear, though. Here are some common ones:

  • Your gas cap is either loose or incorrectly attached
  • Your gas cap does not meet vehicle manufacturer standards
  • You have a tiny leak, crack or hole in a fuel vapor hose or tube
  • You have a different type of leak somewhere in the EVAP system
  • You have a faulty vent or purge valve
  • You have a bad vent seal
  • You have an unreliable leak detection pump in the EVAP system

Potential Simple Resolutions

Now that you understand the trouble code technical description, you need to know how to repair your vehicle.

If you see a P0442 evaporative emission system leak detected code, you may be able to resolve the problem without much effort. The easiest solution may be to remove and reaffix the gas cap. Once you do, clear the code on the OBD-II diagnostic scanner and drive for a few days. If the code does not return, your gas cap likely was the culprit.

Of course, there is a chance that your gas cap either has worn out or is not compatible with your EVAP system. If so, you should replace the cap with an OEM equivalent available at your local AutoZone. Then, clear the code, test drive your vehicle and see if the check engine light illuminates again.

If tightening or replacing your vehicle’s fuel cap does not remedy the problem, you should check out your EVAP system. A visual inspection should alert you to tears, holes or cracks in the tubes and hoses throughout the system. If you see any, replace the damaged part.

Potential Advanced Resolutions

As you may suspect, sometimes tinkering with the fuel cap and visually inspecting the EVAP system do not resolve a P0442 DTC. If that is the case, you may need to do additional work to find the leak. An advanced scan tool allows you to perform an EVAP leak examination. This process may help you find leaks that are 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 may remedy the situation. If that fails, you may need to perform a smoke test to uncover where the EVAP system is leaking. (An advanced scan tool and smoke leak detectors are used by professional auto repair technicians).

Whether a simple or advanced approach takes care of your evaporative emission system leak detected 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.

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