Chevrolet 2006 Avalanche Owner's Manual page 360

When replacing the fuel cap, turn it clockwise until it
clicks. It will require more effort to turn the fuel cap on
the last turn as you tighten it. Make sure the cap is
fully installed. The diagnostic system can determine if
the fuel cap has been left off or improperly installed. This
would allow fuel to evaporate into the atmosphere.
See Malfunction Indicator Lamp on page 3-40.
The TIGHTEN FUEL CAP message will be displayed on
the Driver Information Center (DIC) if the fuel cap is
not properly installed. See DIC Warnings and Messages
on page 3-50 for more information.
5-10
CAUTION:
{
If a fire starts while you are refueling, do not
remove the nozzle. Shut off the flow of fuel by
shutting off the pump or by notifying the
station attendant. Leave the area immediately.
Notice: If you need a new fuel cap, be sure to get
the right type. Your dealer can get one for you.
If you get the wrong type, it may not fit properly.
This may cause your malfunction indicator lamp to
light and may damage your fuel tank and emissions
system. See Malfunction Indicator Lamp on
page 3-40.