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.

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.

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.

If none of these solutions work, give us a call at Callahan Automotive today to schedule an inspection of your vehicle.