Most newer vehicles come equip with an internal self-diagnostic system called an On-Board Diagnostics (OBD). The OBD sources problems within your vehicle and uses numerical coding to identify the problem. If your Chrysler PT Cruiser is displaying the OBD code P0442, a leak has been detected in your evaporative system. There are a few things that can cause the P0442 code; troubleshoot the problem using an OBD reader and a smoke machine.
Check the gas cap to make sure it is screwed on tightly. In newer vehicles, a loose gas cap will set off the "Check engine" light. If the seal of the gas cap is broken, the gas cap needs to be replaced.
Use an OBD reader to see if you have a bad oxygen (O2) sensor. O2 sensors work with the the fuel injection system to calculate oxygen consumption in the exhaust. If your vehicle has a faulty O2 sensor your vehicle is unable to meter fuel.
Use a diagnostic tool such as a smoke machine to source the leak. Place the needle of the smoke machine into the EVAP service port or hook it up to the battery. Use a few line locks to block off line going to the fuel canister. Turn the machine on and roll it under the vehicle. The smoker uses a food-grade oil laced with reflective trace elements that create a fine mist or smoke, which seep through leaks under pressure. Once you source the leak, replace the line or hose.
