"SES light" Small emissions leak "code p0442"

[jbizel]

About a month ago I had my SES light go on and I took it to the auto parts store and they said it was a small emissions leak. I am not sure of the code though. I took my car to the shop and they said that a sensor that had something to do with the exhaust was bad or unplugged.

My SES light came back on about about a week ago and I had it tested and it said the same thing. "Small emissions leak" This time I got the code and its P0442. The shop is closed today and tomarrow so I was just wondering if anyone knew what and where the sensor is located? Or if its the same thing?

[richtazz]

A small emissions leak could be anything from a loose/defective gas cap to a cracked line running to/from the vapor canister to a defective purge/vent solenoid. If tightening/changing the gas cap doesn't fix it, a smoke test at a garage may be the best option to eliminate unnecessary parts swapping.

[jbizel]

Last time I had it in the shop they said it was a senor that had to do with the exhaust though. So I am just guessing that it is the same thing that it was before. What type of sensors have to do with the exhaust? Just the 02 sensor?

[richtazz]

I'm not saying it's not possilbe, but I've never heard of an oxygen sensor (the only emission related sensor(s) located in the exhaust) tripping a P0442 code. The vent solenoid, canister purge solenoid or gas cap/filler hose assemblies are the most common cause.

[jbizel]

That may be true. I am just going by what I was told. I am going to see if I can get it fixed soon and then I'll post to let you know what it was. THanks

[BNaylor]

Yeah, that doesn't sound right. I've never heard of an 02 sensor causing an evaporative emissions problem. Sometimes you have to take what an auto mechanic tells you with a grain of salt no matter how much you may trust them with your car. DTC P0442 is really the worst evaporative emission fault to have because it is not easy to troubleshoot without proper diagnostics and testing equipment. It is centered around a small leak between the gas filler cap all the way to the purge solenoid at the engine compartment.

Here is a recent teck link posted by GMMerlin that may be helpful:

http://www.automotiveforums.com/vbul...d.php?t=622474

If all the vacuum lines are good, one component often overlooked is the charcoal cannister due to its bad location by the gas tank. They can develop small leaks and throw that code.

[Piston Pusher]

I have 2000 Grand Prix 3.8 which keeps tripping a P0442 code only on the initial couple of km's of a trip. I erase the code and it does not re-appear till the car cools and proceed on another trip. I have replaced the gas cap with a quality cap, the canister vent solenoid and the purge solenoid in the engine compartment.I'd say if there was a leak the code would appear
on a constant basis just not on the initial cycle search.Stumped on this one. Bruce

[Tech II]

Well it's a small leak that could be anywhere......at a dealership, they would use their scan tool to seal the system, and with a smoke machine attached, they would pressurize the system with smoke....where you see smoke, you have found the leak....