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STARTING AND OPERATING 147
If the transmission becomes extremely hot or is in
danger of overheating, the “Transmission
Temperature Warning Light” may illuminate and
the transmission may operate differently until the
transmission cools down.
NOTE:
Use caution when operating a heavily loaded
ve
hicle at low speeds (such as towing a trailer up a
steep grade, or in stop-and-go traffic) during hot
weather. In these conditions, torque converter slip
can impose a significant additional heat load on
the cooling system. Downshifting the transmission
to the lowest possible gear (when climbing a
grade), or shifting to NEUTRAL (when stopped in
heavy traffic) can help to reduce this excess heat
generation.
During cold temperatures, transmission operation
may be modified depending on engine and
transmission temperature as well as vehicle
speed. This feature improves warm-up time of the
engine and transmission to achieve maximum
efficiency. Engagement of the torque converter
clutch is inhibited until the transmission fluid is
warm
Ú page 149. On Pickup models with 68RFE
transmission, top overdrive gear is also inhibited
u
n
til the transmission fluid is warm, and during
extremely cold temperatures (-16°F [-27°C] or
below), operation may briefly be limited to first and
direct gears only. On trucks with AS69RC
transmission, FIFTH and SIXTH gears may be
inhibited briefly on cold starts below 41°F (5°C),
and during very cold temperatures (-4°F [-20°C] or
below), operation may briefly be limited to third
gear only. During this condition, the ability of the
vehicle to accelerate under heavily loaded
conditions may be reduced. In all cases, normal
operation will resume once the transmission
temperature has risen to a suitable level.
Transmission Limp Home Mode
Transmission function is monitored electronically
for abnormal conditions. If a condition is detected
that could result in transmission damage,
Transmission Limp Home Mode is activated. In this
mode, the transmission remains in FOURTH gear
(for 68RFE transmission) or THIRD gear (for
AS69RC transmission) regardless of which forward
gear is selected. If an AS69RC-equipped truck
enters Limp Home Mode at highway speeds, it will
initially engage FIFTH gear, until the vehicle slows
to a speed where third gear can be engaged. PARK,
REVERSE, and NEUTRAL will continue to operate.
The Malfunction Indicator Light (MIL) may be
illuminated. Limp Home Mode allows the vehicle to
be driven to an authorized dealer for service
without damaging the transmission.
In the event of a momentary problem, the
tr
ansmission can be reset to regain all forward
gears by performing the following steps:
1. Stop the vehicle.
2
. S
hift the transmission into PARK.
3
. Turn the ignition OFF.
4
. Wait approximately 10 seconds.
5
. Restart the engine.
6
. S
hift into the desired gear range. If the
p
roblem is no longer detected, the
transmission will return to normal operation.
NOTE:
Even if the transmission can be reset, we
re
commend that you visit an authorized dealer at
your earliest possible convenience. An authorized
dealer has diagnostic equipment to assess the
condition of your transmission. If the transmission
cannot be reset, authorized dealer service is
required.
Electronic Range Select (ERS) Operation
The Electronic Range Select (ERS) shift control
allows the driver to limit the highest available gear
when the transmission is in DRIVE. For example, if
you set the transmission gear limit to FOURTH
gear, the transmission will not shift above FOURTH
gear, but will shift through the lower gears
normally.
You can switch between DRIVE and ERS mode at
an
y vehicle speed. When the gear selector is in the
DRIVE position, the transmission will operate
automatically, shifting between all available gears.
Tapping the ERS (-) switch will activate ERS mode,
display the current gear in the instrument cluster,
4
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