OPERATION
If opening the throttle alone cannot maintain the
set speed and the vehicle speed drops more than
three mph below the set speed, the transmission will
downshift to third gear. If the vehicle continues to
lose speed, by more than 6 mph, the transmission
will downshift again maintain the set speed. After
the vehicle encounters a less-steep grade, or has
crested the grade (reduced the load on the power-
train) and can maintain the set speed at a reduced
throttle position, the transmission will upshift, as
appropriate, until the set speed can be maintained in
Overdrive.
DOWNSHIFT DELAY
DESCRIPTION
Downshift delay features have been added to
reduce the number and frequency of downshifts when
operating in hilly or mountainous country.
OPERATION
While operating, interactive speed control delays or
avoids downshifts by allowing up to nearly wide open
throttle without the TCM scheduling a downshift. If
the interactive speed control is not engaged or the
throttle is manually overridden by the driver while
interactive speed control is engaged, the downshift
delay feature is not activated.
Torque converter lock and unlock shifts are not
affected by the downshift delay feature and will occur
at the same throttle angle at a given speed regard-
less of whether interactive speed control operates or
not.
GRADE HUNTING
DESCRIPTION
All vehicles equipped with a four speed automatic
transmission have a grade hunting feature for the
2nd to 3rd gear upshift and the 3rd to Overdrive
upshift.
OPERATION
The TCM identifies the powertrain loading condi-
tions and selects the proper gear to maintain the cur-
rent vehicle speed. Under moderate loading
conditions the transaxle will stay in 3rd gear until
the top of the grade is reached or the powertrain
loading is reduced.
If powertrain loading is severe, the transaxle may
shift into 2nd gear and remain there until power-
train loading is reduced, then a 2nd to 3rd gear
upshift will be scheduled. Grade hunting features
always operate regardless of whether or not the
interactive speed control is engaged. If the interac-
tive speed control is not engaged and power-
train loading is not reduced, the driver may
have to completely lift off of the throttle before
an upshift will occur. If the driver does lift off the
throttle to induce an upshift under these conditions,
vehicle speed will reduce and the Overdrive to 3rd
and 3rd to 2nd gear downshifts will reoccur when the
throttle is reapplied. If grade hunting is repeatedly
induced by the driver, transaxle damage may result.
AUTOMATIC SPEED CONTROL OVERSPEED
REDUCTION
DESCRIPTION
Transmission control software includes an auto-
matic speed control overspeed reduction feature. This
maintains vehicle speed at the selected set point
when descending a grade.
OPERATION
The Transmission Control Module (TCM) first
senses that the speed control is set. If the set speed
is exceeded by more than 4 mph (6.5 km/hr) and the
throttle is closed, the TCM causes the transaxle to
downshift to THIRD gear. After downshifting, the
automatic speed control resumes normal operation.
To ensure that an upshift is appropriate after the set
speed is reached, the TCM waits until the speed con-
trol system opens the throttle at least 6 degrees
before upshifting to OVERDRIVE again.
If the driver applies the brakes, canceling auto-
matic speed control operation with the transaxle still
in THIRD gear, the TCM maintains this gear until
the driver opens the throttle at least 6 degrees to
avoid an inappropriate upshift. The upshift is also
delayed for 2.5 seconds after reaching the 6 degrees
throttle opening in anticipation that the driver might
open the throttle enough to require THIRD gear.
This will avoid unnecessary and disturbing transmis-
sion cycling. If the automatic speed control RESUME
feature is used after braking, the upshift is delayed
until the set speed is achieved to reduce cycling and
provide better response.
BRAKE LAMP SWITCH
DESCRIPTION
The switch is mounted on the brake pedal mount-
ing bracket under the instrument panel.
OPERATION
Vehicles equipped with the speed control option use
a dual function brake lamp switch. The PCM moni-
tors the state of the dual function brake lamp switch.
Refer to the Brake section for more information on
LH VEHICLE SPEED CONTROL SYSTEM 8H - 3
DESCRIPTION AND OPERATION (Continued)
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