2002 Jeep Grand Cherokee V8 116k miles.

When you turn the engine on you can hear a noticeable hissing sound.
I seems to originate near the left rear wheel. I didn't get the
chance to further locate the origin of the noise as I will have to get
under the car for that and I only briefly looked at in the parking
lot. It's where also the fuel door is.

Could that have to do with anything with the error codes I am reading
P0442/P0455?
P0442 Evaporative Emission Control System Leak Detected (small leak)
P0455 Evaporative Emission Control System Leak Detected (gross leak)

Found this: http://www.obd-codes.com/forums/viewtopic.php?f=6&t=3970
Maybe a damaged hose and hence the hissing noise?

Any help is greatly appreciated.
Axel

the evap. system is indeed in the left rear quarter panel and a vacumm
hose leak can and will set the lite so if you are hearing a hissing noise
make sure it's not under the hood there is a few on the engine that fall
off easy esp. on the 4.0
remove the gas cap and look at the center white plastic and if you see
rust or the color of it repalce the cap it's leaking to atmosphere

axel wrote:

Update: Fixed.

I don't think the following answer I got was posted here:
" If you remove the left rear wheel and the inner wheelwell splash
shield,
you'll be able to see a maze of hoses and valves that make up the ORVR
and
evap leak detection pump systems in that LR fender area.

There is a vacuum line that runs from the engine to that pump and it
is
common for it to split or crack over time, that is likely the hissing
noise
you hear. The codes you are getting are probably related, either due
to that
vacuum leak (the pump can't work properly) or another related line in
that
area is cracked or leaking.
The pump assembly is mounted on a bracket there, so you need to
loosen but
not remove the bolts and swing it down to reach all the various hoses.
If
the bolts are rusted and can't be removed, you'll have to remove the
rear
bumper cover (fascia) to get at everything."

After removing the inner wheelwell splash shield I already saw the
cracked hose. I didn't even have to mess with the pump bracket.
Got 4ft of 1/4" hose at the parts store for $5.16 and a few new rivets
($6) for the splash shield (they all broke while taking it off),
replaced the hose, put the splash shield back on, reset the engine
codes and 2hrs later it is fixed.

Thanks for all your help.
Axel