2021 JEEP WRANGLER UNLIMITED brake

78
(Continued)
SAFETY
SAFETY FEATURES
Anti-Lock Brake System (ABS)
The Anti-Lock Brake System (ABS) provides
increased vehicle stability and brake perfor-
mance under most braking conditions. The
system automatically prevents wheel lock,
and enhances vehicle control during braking.
The ABS performs a self-check cycle to
ensure that the ABS is working properly each
time the vehicle is started and driven. During
this self-check, you may hear a slight
clicking sound as well as some related motor
noises.
ABS is activated during braking when the
system detects one or more wheels begin to
lock. Road conditions such as ice, snow,
gravel, bumps, railroad tracks, loose debris,
or panic stops may increase the likelihood of
ABS activation(s). You also may experience the following when
ABS activates:
The ABS motor noise (it may continue to
run for a short time after the stop)
The clicking sound of solenoid valves
Brake pedal pulsations
A slight drop of the brake pedal at the end
of the stop
These are all normal characteristics of ABS.
ABS is designed to function with the Original
Equipment Manufacturer (OEM) tires. Modi-
fication may result in degraded ABS perfor -
mance.
Anti-Lock Brake Warning Light
The yellow “Anti-Lock Brake Warning Light”
will turn on when the ignition is placed in the
ON/RUN mode and may stay on for as long
as four seconds.
WARNING!

The ABS contains sophisticated electronic
equipment that may be susceptible to inter -
ference caused by improperly installed or
high output radio transmitting equipment.
This interference can cause possible loss of
anti-lock braking capability. Installation of
such equipment should be performed by
qualified professionals.

Pumping of the Anti-Lock Brakes will
diminish their effectiveness and may
lead to a collision. Pumping makes the
stopping distance longer. Just press
firmly on your brake pedal when you
need to slow down or stop.
The ABS cannot prevent the natural laws
of physics from acting on the vehicle, nor
can it increase braking or steering effi -
ciency beyond that afforded by the
condition of the vehicle brakes and tires
or the traction afforded.
The ABS cannot prevent collisions,
including those resulting from excessive
speed in turns, following another vehicle
too closely, or hydroplaning.
The capabilities of an ABS equipped
vehicle must never be exploited in a
reckless or dangerous manner that could
jeopardize the user’s safety or the safety
of others.
WARNING! (Continued)
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79
If the “Anti-Lock Brake Warning Light”
remains on or comes on while driving, it indi-
cates that the anti-lock portion of the brake
system is not functioning and that service is
required. However, the conventional brake
system will continue to operate normally if
the “Anti-Lock Brake Warning Light” is on.
If the “Anti-Lock Brake Warning Light” is on,
the brake system should be serviced as soon
as possible to restore the benefits of
anti-lock brakes. If the “Anti-Lock Brake
Warning Light” does not come on when the
ignition is placed in the ON/RUN mode, have
the light repaired as soon as possible.
Electronic Brake Control (EBC) System

Your vehicle is equipped with an advanced
Electronic Brake Control (EBC) system. This
system includes Electronic Brake Force Distri -
bution (EBD), Anti-Lock Brake System (ABS),
Brake Assist System (BAS), Hill Start Assist
(HSA), Traction Control System (TCS), Elec-
tronic Stability Control (ESC), and Electronic
Roll Mitigation (ERM). These systems work
together to enhance both vehicle stability and
control in various driving conditions.
Your vehicle may also be equipped with
Trailer Sway Control (TSC), Ready Alert
Braking (RAB), Rain Brake Support (RBS),
and Hill Descent Control (HDC).
Brake System Warning Light
The red “Brake System Warning Light” will
turn on when the ignition is placed in the
ON/RUN mode and may stay on for as long
as four seconds.
If the “Brake System Warning Light”
remains on or comes on while driving, it indi
-
cates that the brake system is not func -
tioning properly and that immediate service
is required. If the “Brake System Warning
Light” does not come on when the ignition is
placed in the ON/RUN mode, have the light
repaired as soon as possible.
Brake Assist System (BAS)
The Brake Assist System (BAS) is designed
to optimize the vehicle’s braking capability
during emergency braking maneuvers. The
system detects an emergency braking situa -
tion by sensing the rate and amount of brake
application and then applies optimum pres -
sure to the brakes. This can help reduce
braking distances. The BAS complements
the Anti-Lock Brake System (ABS). Applying the brakes very quickly results in the best
BAS assistance. To receive the benefit of the
system, you must apply continuous braking
pressure during the stopping sequence, (do
not “pump” the brakes). Do not reduce brake
pedal pressure unless braking is no longer
desired. Once the brake pedal is released,
the BAS is deactivated.
WARNING!
The Brake Assist System (BAS) cannot
prevent the natural laws of physics from
acting on the vehicle, nor can it increase
the traction afforded by prevailing road
conditions. BAS cannot prevent collisions,
including those resulting from excessive
speed in turns, driving on very slippery
surfaces, or hydroplaning. The capabilities
of a BAS-equipped vehicle must never be
exploited in a reckless or dangerous
manner, which could jeopardize the user's
safety or the safety of others.
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80
Electronic Brake Force Distribution (EBD)
The Electronic Brake Force Distribution
(EBD) manages the distribution of the
braking torque between the front and rear
axles by limiting braking pressure to the rear
axle. This is done to prevent overslip of the
rear wheels to avoid vehicle instability, and
to prevent the rear axle from entering ABS
before the front axle.
Electronic Roll Mitigation (ERM)
Electronic Roll Mitigation (ERM) anticipates
the potential for wheel lift by monitoring the
driver’s steering wheel input and the speed
of the vehicle. When ERM determines that
the rate of change of the steering wheel
angle and vehicle’s speed are sufficient to
potentially cause wheel lift, it then applies
the appropriate brake and may also reduce
engine power to lessen the chance that
wheel lift will occur. ERM can only reduce
the chance of wheel lift occurring during
severe or evasive driving maneuvers; it
cannot prevent wheel lift due to other
factors, such as road conditions, leaving the
roadway, or striking objects or other vehicles.NOTE:
ERM is disabled anytime the ESC is in “Full
Off” mode (if equipped). Refer to “Electronic
Stability Control (ESC)” in this section for a
complete explanation of the available ESC
modes.
Electronic Stability Control (ESC)
Electronic Stability Control (ESC) enhances
directional control and stability of the
vehicle under various driving conditions.
ESC corrects for oversteering or under
-
steering of the vehicle by applying the brake
of the appropriate wheel(s) to assist in coun -teracting the oversteer or understeer condi
-
tion. Engine power may also be reduced to
help the vehicle maintain the desired path.
ESC uses sensors in the vehicle to determine
the vehicle path intended by the driver and
compares it to the actual path of the vehicle.
When the actual path does not match the
intended path, ESC applies the brake of the
appropriate wheel to assist in counteracting
the oversteer or understeer condition.
Oversteer — when the vehicle is turning
more than appropriate for the steering
wheel position.
Understeer — when the vehicle is turning
less than appropriate for the steering
wheel position.
The “ESC Activation/Malfunction Indicator
Light” located in the instrument cluster will
start to flash as soon as the ESC system
becomes active. The “ESC Activation/
Malfunction Indicator Light” also flashes
when the TCS is active. If the “ESC Activa -
tion/Malfunction Indicator Light” begins to
flash during acceleration, ease up on the
accelerator and apply as little throttle as
possible. Be sure to adapt your speed and
driving to the prevailing road conditions.
WARNING!
Many factors, such as vehicle loading,
road conditions and driving conditions,
influence the chance that wheel lift or
rollover may occur. ERM cannot prevent all
wheel lift or roll overs, especially those
that involve leaving the roadway or striking
objects or other vehicles. The capabilities
of an ERM-equipped vehicle must never
be exploited in a reckless or dangerous
manner which could jeopardize the user's
safety or the safety of others.
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83
The “ESC Activation/Malfunction Indicator
Light” (located in the instrument cluster)
starts to flash as soon as the tires lose trac-
tion and the ESC system becomes active.
The “ESC Activation/Malfunction Indicator
Light” also flashes when TCS is active. If the
“ESC Activation/Malfunction Indicator
Light” begins to flash during acceleration,
ease up on the accelerator and apply as little
throttle as possible. Be sure to adapt your
speed and driving to the prevailing road
conditions.
NOTE:
The “ESC Activation/Malfunction Indi -
cator Light” and the “ESC OFF Indicator
Light” come on momentarily each time
the ignition is turned ON.
Each time the ignition is turned ON, the
ESC system will be on even if it was turned
off previously.
The ESC system will make buzzing or
clicking sounds when it is active. This is
normal; the sounds will stop when ESC
becomes inactive following the maneuver
that caused the ESC activation. The “ESC OFF Indicator Light”
indicates the customer has elected
to have the Electronic Stability
Control (ESC) in a reduced mode.
Hill Descent Control (HDC) — If Equipped
Hill Descent Control (HDC) is intended for
low speed off road driving while in 4L Range.
HDC maintains vehicle speed while
descending hills during various driving situa
-
tions. HDC controls vehicle speed by actively
controlling the brakes.
HDC has three states:
1. Off (feature is not enabled and will not activate)
2. Enabled (feature is enabled and ready but activation conditions are not met, or
driver is actively overriding with brake or
throttle application)
3. Active (feature is enabled and actively controlling vehicle speed) Enabling HDC
HDC is enabled by pushing the HDC switch,
but the following conditions must also be
met to enable HDC:
Driveline is in 4L Range
Vehicle speed is below 5 mph (8 km/h)
Park brake is released
Driver door is closed (If doors are
attached, then door must be closed. If
doors are detached, then driver seatbelt
must be buckled)
Activating HDC
Once HDC is enabled it will activate auto -
matically if driven down a grade of sufficient
magnitude. The set speed for HDC is select -
able by the driver, and can be adjusted by
using the gear shift +/-. The following
summarizes the HDC set speeds:
HDC Target Set Speeds
P = No set speed. HDC may be enabled
but will not activate
R = 0.6 mph (1 km/h)
N = 1.2 mph (2 km/h)
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84
D = 0.6 mph (1 km/h)
1st = 0.6 mph (1 km/h)
2nd = 1.2 mph (2 km/h)
3rd = 1.8 mph (3 km/h)
4th = 2.5 mph (4 km/h)
5th = 3.1 mph (5 km/h)
6th = 3.7 mph (6 km/h)
7th = 4.3 mph (7 km/h)
8th = 5.0 mph (8 km/h)
9th = 5.6 mph (9 km/h) – If Equipped
NOTE:
During HDC the +/- shifter input is used for
HDC target speed selection, but will not
affect the gear chosen by the transmission.
When actively controlling HDC, the transmis -
sion will shift appropriately for the
driver-selected set speed and corresponding
driving conditions. Driver Override
The driver may override HDC activation with
throttle or brake application at anytime.
Deactivating HDC
HDC will be deactivated but remain available
if any of the following conditions occur:
Driver overrides HDC set speed with
throttle or brake application
Vehicle speed exceeds 20 mph (32 km/h)
but remains below 40 mph (64 km/h)
Vehicle is on a downhill grade of insuffi -
cient magnitude, is on level ground, or is
on an uphill grade
Vehicle is shifted to PARK (P)
Disabling HDC
HDC will be deactivated and disabled if any
of the following conditions occur:
The driver pushes the HDC switch
The driveline is shifted out of 4L Range
The park brake is applied
Driver door opens (Driver door opens if
doors are attached or driver seatbelt is
unbuckled if doors are detached)
The vehicle is driven greater than 20 mph
(32 km/h) for greater than 70 seconds
The vehicle is driven greater than 40 mph
(64 km/h) (HDC exits immediately)
HDC detects excessive brake temperature
Feedback To The Driver
The instrument cluster has an HDC icon and
the HDC switch has an indicator light, which
offers feedback to the driver about the state
HDC is in.
The cluster icon and switch indicator light
will illuminate and remain on solid when
HDC is enabled or activated. This is the
normal operating condition for HDC.
The cluster icon and switch indicator light
will flash for several seconds then extin -
guish when the driver pushes the HDC
switch but enable conditions are not met.

The cluster icon and switch indicator light will
flash for several seconds then extinguish when
HDC disables due to excess speed.

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85
The cluster icon and switch indicator light
will flash when HDC deactivates due to
overheated brakes. The flashing will stop
and HDC will activate again once the
brakes have cooled sufficiently.
Hill Start Assist (HSA)

The Hill Start Assist (HSA) system is designed to
mitigate roll back from a complete stop while on
an incline. If the driver releases the brake while
stopped on an incline, HSA will continue to hold
the brake pressure for a short period. If the driver
does not apply the throttle before this time
expires, the system will release brake pressure
and the vehicle will roll down the hill as normal.
The following conditions must be met in
order for HSA to activate:
The feature must be enabled
The vehicle must be stopped
Park brake must be off
Driver door must be closed. (If the doors
are attached, then the door must be
closed. If the doors are detached then the
driver's seatbelt must be buckled)
The vehicle must be on a sufficient grade
The gear selection must match vehicle
uphill direction (i.e., vehicle facing uphill
is in forward gear; vehicle backing uphill is
in REVERSE (R) gear)
HSA will work in REVERSE gear and all
forward gears. The system will not activate
if the transmission is in PARK (P) or
NEUTRAL (N). For vehicles equipped with
a manual transmission, if the clutch is
pressed, HSA will remain active.
Disabling And Enabling HSA
This feature can be turned on or turned off.
To change the current setting, refer to
“Instrument Cluster Display” in “Getting To
Know Your Instrument Panel” for further
information.
WARNING!
HDC is only intended to assist the driver in
controlling vehicle speed when descending
hills. The driver must remain attentive to
the driving conditions and is responsible
for maintaining a safe vehicle speed.
WARNING!
There may be situations where the Hill
Start Assist (HSA) will not activate and
slight rolling may occur, such as on minor
hills or with a loaded vehicle, or while
pulling a trailer. HSA is not a substitute for
active driving involvement. It is always the
driver’s responsibility to be attentive to
distance to other vehicles, people, and
objects, and most importantly brake
operation to ensure safe operation of the
vehicle under all road conditions. Your
complete attention is always required
while driving to maintain safe control of
your vehicle. Failure to follow these
warnings can result in a collision or serious
personal injury.
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86
Towing With HSA
HSA will also provide assistance to mitigate
roll back while towing a trailer.
Ready Alert Braking (RAB)
Ready Alert Braking (RAB) may reduce the
time required to reach full braking during
emergency braking situations. It anticipates
when an emergency braking situation may
occur by monitoring how fast the throttle is
released by the driver. The Electronic Brake
Control (EBC) system will prepare the brake
system for a panic stop.
Rain Brake Support (RBS)
Rain Brake Support (RBS) may improve
braking performance in wet conditions. It
will periodically apply a small amount of
brake pressure to remove any water buildup
on the front brake rotors. It functions when
the windshield wipers are in LO or HI speed.
When RBS is active, there is no notification
to the driver and no driver interaction is
required.
Trailer Sway Control (TSC)
Trailer Sway Control (TSC) uses sensors in
the vehicle to recognize an excessively
swaying trailer and will take the appropriate
actions to attempt to stop the sway. TSC will
become active automatically once an exces-
sively swaying trailer is recognized.

NOTE:
TSC cannot stop all trailers from swaying.
Always use caution when towing a trailer and
follow the trailer tongue weight recommenda-
tions. Refer to “Trailer Towing” in “Starting
And Operating” for further information.

When TSC is functioning, the “ESC Activa -
tion/Malfunction Indicator Light” will flash,
the engine power may be reduced and you
may feel the brakes being applied to indi -
vidual wheels to attempt to stop the trailer
from swaying. TSC is disabled when the ESC
system is in the “Partial Off” or “Full Off”
modes.
WARNING!
If you use a trailer brake controller with
your trailer, the trailer brakes may be
activated and deactivated with the brake
switch. If so, there may not be enough
brake pressure to hold both the vehicle
and the trailer on a hill when the brake
pedal is released. In order to avoid
rolling down an incline while resuming
acceleration, manually activate the
trailer brake or apply more vehicle brake
pressure prior to releasing the brake
pedal.
HSA is not a parking brake. Always apply
the parking brake fully when exiting your
vehicle. Also, be certain to place the
transmission in PARK (P).
Failure to follow these warnings can
result in a collision or serious personal
injury. WARNING!
If TSC activates while driving, slow the
vehicle down, stop at the nearest safe
location, and adjust the trailer load to
eliminate trailer sway.
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87
Traction Control System (TCS)

The Traction Control System (TCS) monitors the
amount of wheel spin of each of the driven
wheels. If wheel spin is detected, the TCS may
apply brake pressure to the spinning wheel(s) and/
or reduce engine power to provide enhanced
acceleration and stability. A feature of the TCS,
Brake Limited Differential (BLD), functions
similar to a limited slip differential and controls
the wheel spin across a driven axle. If one wheel
on a driven axle is spinning faster than the other,
the system will apply the brake of the spinning
wheel. This will allow more engine torque to be
applied to the wheel that is not spinning. BLD
may remain enabled even if TCS and Electronic
Stability Control (ESC) are in a reduced mode.

AUXILIARY DRIVING
SYSTEMS
Blind Spot Monitoring (BSM) — If
Equipped
The Blind Spot Monitoring (BSM) system
uses two radar-based sensors, located inside
the taillights, to detect highway licensable
vehicles (automobiles, trucks, motorcycles,
etc.) that enter the blind spot zones from the
rear/front/side of the vehicle.Rear Detection Zones

When the vehicle is started, the BSM warning
light will momentarily illuminate in both outside
rear view mirrors to let the driver know that the
system is operational. The BSM system sensors
operate when the vehicle is in any forward gear or
REVERSE (R) and enters standby mode when the
vehicle is in PARK (P).
The BSM detection zone covers approximately
one lane width on both sides of the vehicle, 12 ft
(3.8 m). The zone length starts at the outside rear
view mirror and extends approximately 10 ft
(3 m) beyond the rear bumper of the vehicle. The
BSM system monitors the detection zones on both
sides of the vehicle when the vehicle speed
reaches approximately 6 mph (10 km/h) or higher and will alert the driver of vehicles in these areas.
NOTE:
The BSM system DOES NOT alert the
driver about rapidly approaching vehicles
that are outside the detection zones.
The BSM system detection zone DOES
NOT change if your vehicle is towing a
trailer. Therefore, visually verify the adja-
cent lane is clear for both your vehicle and
trailer before making a lane change. If the
trailer or other object (i.e., bicycle, sports
equipment) extends beyond the side of
your vehicle, this may result in the BSM
warning light remaining illuminated the
entire time the vehicle is in a forward gear.
The Blind Spot Monitoring (BSM) system
may experience drop outs (blinking on and
off) of the side mirror Warning Indicator
lamps when a motorcycle or any small
object remains at the side of the vehicle
for extended periods of time (more than a
couple of seconds).
The area on taillights, where the radar
sensors are located, must remain free of
snow, ice, and dirt/road contamination so
that the BSM system can function properly.
Do not block the taillights where the radar
sensors are located with foreign objects
(bumper stickers, bicycle racks, etc.).
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