Engine Code P 0442

1) Small leak detected in evaporitive purge system. 2) Apart from the obvious, check the petrol tank fuel cap.

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

It means there is a leak in the Evaporative Emissions Control System.

Put the gas cap on securely.

Check it out, P0442 OBD Trouble Code

Technical Description Evaporative Emission Control System Leak Detected (small leak)

What does that mean? This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Symptoms You likely won't notice any drivability problems.

Causes A code P0442 most likely means one or more of the following has happened:

A loose or improperly affixed gas cap A non-conforming gas cap (i.e. not factory/original brand) A small leak/hole in a fuel vapor hose/tube Other small leak in EVAP system Faulty vent o-ring seal

Possible Solutions With a P0442, the most common repair is to:

Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back. Otherwise, replace the gas cap, or Inspect the EVAP system for cuts/holes in tubes/hoses

Here is the OBD Website,

Thanks folks. I went and re affixed the gas cap and I'll take it out for a run later, likely tomorrow, and then recheck the codes. When I opened it up, it made a big old sucking sound. I don't know if this is normal tho (here in NJ we are not allowed to pump our own gas, thank the gods, the hazardous material that it is).

The real reason that I will take it for a run later is it is now drying out from being soaked from today's rainpour. I thought that I could get away with just the bikini top - LOL on me. Actually, I was fine with my doors put back on, but that gap between the roll bar and the door was the funnel point for all of the rain from the top and I ended up with 3 inches of water on the passenger side when I got home (mostly left turns in the beginning dumped most of it that way). I was dry tho. Seats all wet, the way back all soaked from shoving the soaked over-cover in there. I have come to realize that that over-cover is water resistant, not water proof [grin]. Therefore, I want to let it sit in the sun tomorrow for a bit. ;-] Tomes

Well, I like to believe the gas pumping professionals are highly trained, and they know how to put the gas cap back on, as tricky as that might be. Since these professionals are the cream of the crop, then you may have an actual leak somewhere, or your professional missed training the day they put gas caps on. The giant sucking sound is normal, this means that the system is sealed, which is counter to the P0442 code.

I'd reset the codes and twist the gas cap a few clicks, and wait for the code to pop up again.

yeah, I know - I was being a bit facetious too. I do like not having to do it however - it keeps me from getting smelly and in the vehicle on bad weather days.

Once I run the Jeep around for a bit later on I will report back. Thanks again folks. Tomes

I am thinking that all my incumbent gas is still in there as my gauge reading is unaffected, and thanks Bill. Tomes

I knew it. I was just goofing....

OK, so it has been a couple of days now [all dried out - went to Black Potatoe folk music festival today] put the gas cap on and off a few times, still get the code. I looked around in a cursory manner under the hood, not really knowing what to look for, and see nothing out of the ordinary in the way of vacuum lines that I find in there.

What is next for me to do?

Thanks again, Tomes

Thanks, I did not know this. Today's trip was about 15 minutes each way. Tomorrow to work and back will be a better run for this. Tomes

You have to physically reset the code, or wait for several (I think the number is in the range of ~40) start-cycles for it to go out on it's own. It will not have gone out by now, even if the gas cap was not secured when the code came up.

Well I guess that is where I am then, off to the land of the 40. I'm up to maybe 10 now.... Thanks. I suppose physically setting the code is something I am not to do?

Or you can disconnect the battery which will clear the error codes.

That is a false assumption. There is no reason you can't reset the code. I am not sure, but I think you can do it by unplugging the battery for something like 5 minutes.