GMC 2007 Sierra 1500 Pickup Owner's Manual page 463

All engine speed values listed above are factory
preset values. With the exception of the TCC
lockup speed (1,100 rpm) and the "tap" increment
(100 rpm), all of these values are programmable
and can be adjusted by your dealer or body
upfitter. If the PTO software settings do not match
the settings shown here, then they may have
already been altered in order to satisfy the
requirements of the installed PTO system and
body equipment.
When the PTO switch is turned on, the engine is
limited to 2,200 rpms. If there are no accessories
installed on the vehicle, make sure the PTO switch
is turned off.
Step-Bumper Pad
Your vehicle has a rear step bumper with a rear
step pad at the center of the bumper.
If your step-bumper has only one cutout circle,
you will have to cut out the circle, then remove it to
install the trailer ball.
If you will be using the
bumper to tow a trailer,
and your step-bumper
has three cutout circles,
you must push out the
center cutout circle to
install the trailer ball.
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