Jeep Grand Cherokee 2013 Owner's Manual page 480

478 STARTING AND OPERATING
Electronic Range Select (ERS) Operation
The Electronic Range Select (ERS) shift control allows the
driver to limit the highest available gear when the shift
lever is in the DRIVE position. For example, if you shift
the transmission into 3 (third gear), the transmission will
never shift above third gear, but will shift down into
second and first gears normally.
Use of ERS (or TOW/HAUL mode) also enables an
additional underdrive gear which is not normally used
during through-gear accelerations. This additional gear
can improve vehicle performance and cooling capability
when towing a trailer on certain grades. In ERS mode,
gears 1 though 3 are underdrive gears, and ERS 4 is direct
drive. ERS 5 and 6 (Overdrive gears ) are the same as the
normal fourth and fifth gears.
You can switch between DRIVE and ERS mode at any
vehicle speed. When the shift lever is in the DRIVE
position, the transmission will operate automatically,
shifting between all available gears. Tapping the shift
lever to the left (-) will activate ERS mode, display the
current gear in the instrument cluster, and maintain that
gear as the top available gear. Once in ERS mode, tapping
the shift lever to the left (-) or right (+) will change the top
available gear. The instrument cluster display will show
the requested top gear limit, however the transmission
will not downshift to the requested gear if doing so
would overspeed the engine. The transmission will
downshift once the vehicle speed has slowed sufficiently.
To exit ERS mode, simply press and hold the shift lever to
the right (+) until "D" is once again displayed in the shift
lever position indicator in the instrument cluster.