Q:

How is code P0442 fixed?

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The on-board diagnostics, or OBD, code P0442 can often be fixed by tightening the gas cap or replacing the gas cap. The code indicates a small leak in the evaporative emissions, or EVAP, system, which is commonly caused by a loose gas cap or a small hole in the cap. Not all EVAP codes can be fixed by replacing the gas cap as there could be leaks in other parts of the car.

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Further troubleshooting solutions include performing an EVAP test or using advanced diagnostic tools. These advanced solutions should typically be done by a professional mechanic.

The OBD system, known as OBD-II in most cars, runs on a vehicle's engine control unit (ECU). It continually runs diagnostic tests to detect malfunctions in the engine. If a problem is found, it stores a code that gives an indication of the issue, which can be read with an OBD-II scanner. While an OBD-II code can have several causes, it still narrows down the problem to a general area, such as the EVAP system or a particular component like a knock sensor.

Pulling the codes off an ECU is generally the first step of a diagnostic process. Once a repair is made, the codes can be reset. The check engine light will return if a new code is found because the problem was not completely fixed.

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