Q: My best friend took her 2002 GMC Envoy to the garage to get an inspection sticker. It failed with error code P0442. The garage owner told her he couldn’t read the code, that he had no idea what was wrong with her vehicle and that she’d have to bring it to a repair shop to figure it out. First, can you please tell me what that code means and provide an estimate of what it will cost to repair? Second, is it true that the garage cannot, in fact, tell her what the code means?
A: I am very upset that the garage owner and inspector had no idea of code P0442. In fact, it should even be printed on the inspection report. They are all supposed to be well-trained in OBD II inspection. Fact is, code 442 is probably about the most common code they see. Simply put, 442 is a small evaporative emission control leak. We can break that down further. Cars since 1995 have systems built into the car that will not let fuel vapors leak into the atmosphere. By a series of hoses, valves and sensors, the computer tests the integrity of the fuel system. First thing I would recommend would be to have you look at the gas cap gasket and the ratcheting mechanism built into the cap. If that checks OK, the car needs to go to a repair shop that is knowledgeable of the emissions system. Once it gets to the shop, the technician will look over the car for split vacuum hoses or unplugged sensors or valves. If all looks good, the technician will hook up a scan tool and electronically close all the evap valves. At that time, the technician will induce smoke into the system to find the leak. If you live near the ocean, I would recommend a close look at the fuel filler neck between the gas tank and the top. They are very prone to rotting out, leaking and setting an evap code such as 442.