On the 2010 Chevy Equinox, the P0442 is a “small” EVAP leak. And the P0455 is a “large” EVAP leak. First and foremost- check the fuel cap. Check the underside of the fuel cap for any cracks or signs of defects that may keep the cap from sealing correctly. If there are any doubts about the inspection of the cap, replace it. Keep in mind, you will need a cap that meets OE Specs. Those “universal” or “locking” fuel caps sold at after market parts stores do not meet OE specs, and will not seal the system correctly. Even putting fuel into the vehicle while it is running can set both of these codes. If you are sure the cap is good, the next course of action is to have the EVAP system “smoked”. This is where a machine forces smoke through the system and any leaks can then be more easily found and repaired. If the smoke test proves no leaks, then next I would recommend looking into the Fuel Tank Pressure Sensor. If this sensor fails and does not read correct pressure, this would simulate a leak in the system. The FTP Sensor is located at the top of the fuel tank, mounted to the top of the fuel pump assembly. Inspect the wire harness to the sensor for any broken or rubbed-through wires before replacing the sensor. A damaged wire is common here.
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