2020 JEEP WRANGLER UNLIMITED light

77
(Continued)
(Continued)
ONBOARD DIAGNOSTIC
SYSTEM — OBD II
Your vehicle is equipped with a sophisticated
Onboard Diagnostic system called OBD II.
This system monitors the performance of the
emissions, engine, and transmission control
systems. When these systems are operating
properly, your vehicle will provide excellent
performance and fuel economy, as well as
engine emissions well within current govern -
ment regulations.
If any of these systems require service, the
OBD II system will turn on the Malfunction
Indicator Light (MIL). It will also store diag -
nostic codes and other information to assist
your service technician in making repairs.
Although your vehicle will usually be drive -
able and not need towing, see an authorized
dealer for service as soon as possible.
Onboard Diagnostic System (OBD II)
Cybersecurity
Your vehicle is required to have an Onboard
Diagnostic system (OBD II) and a connection
port to allow access to information related to
the performance of your emissions controls.
Authorized service technicians may need to
access this information to assist with the
diagnosis and service of your vehicle and
emissions system. For further information, refer to “Cybersecu-
rity” in “Multimedia” in your Owner’s
Manual.
CAUTION!
Prolonged driving with the MIL on could
cause further damage to the emission
control system. It could also affect fuel
economy and driveability. The vehicle
must be serviced before any emissions
tests can be performed.
If the MIL is flashing while the vehicle is
running, severe catalytic converter
damage and power loss will soon occur.
Immediate service is required.
WARNING!
ONLY an authorized service technician
should connect equipment to the OBD II
connection port in order to read the VIN,
diagnose, or service your vehicle.
CAUTION! (Continued)
If unauthorized equipment is connected
to the OBD II connection port, such as a
driver-behavior tracking device, it may:
Be possible that vehicle systems, including safety related systems,could be impaired or a loss of vehicle
control could occur that may result in
an accident involving serious injury
or death.
Access, or allow others to access, information stored in your vehicle
systems, including personal informa-
tion.
WARNING! (Continued)
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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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SAFETY
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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81
(Continued)ESC Operating Modes
NOTE:
Depending upon model and mode of opera-
tion, the ESC system may have multiple
operating modes.
ESC On
“ESC On” is the normal operating mode for
the ESC. Whenever the vehicle is started, the
ESC system will be in this mode. This mode should be used for most driving conditions.
Alternate ESC modes should only be used for
specific reasons as noted in the following
paragraphs.
Partial Off

The “Partial Off” mode is intended for times
when a more spirited driving experience is
desired. This mode may modify TCS and ESC
thresholds for activation, which allows for more
wheel spin than normally allowed. This mode
may be useful if the vehicle becomes stuck.

To enter the “Partial Off” mode, momentarily
push the “ESC OFF” switch and the “ESC
OFF Indicator Light” will illuminate. To turn
the ESC on again, momentarily push the
“ESC OFF” switch and the “ESC OFF Indi
-
cator Light” will turn off.
NOTE:
For vehicles with multiple partial ESC
modes, a momentary button push will toggle
the ESC mode. Multiple momentary button
pushes may be required to return to “ESC
On” mode.
WARNING!
Electronic Stability Control (ESC) cannot
prevent the natural laws of physics from
acting on the vehicle, nor can it increase
the traction afforded by prevailing road
conditions. ESC cannot prevent acci -
dents, including those resulting from
excessive speed in turns, driving on very
slippery surfaces, or hydroplaning. ESC
also cannot prevent accidents resulting
from loss of vehicle control due to inap -
propriate driver input for the conditions.
Only a safe, attentive, and skillful driver
can prevent accidents. The capabilities
of an ESC equipped vehicle must never
be exploited in a reckless or dangerous
manner which could jeopardize the
user’s safety or the safety of others.Vehicle modifications, or failure to prop -
erly maintain your vehicle, may change
the handling characteristics of your
vehicle, and may negatively affect the
performance of the ESC system.
Changes to the steering system, suspen -
sion, braking system, tire type and size
or wheel size may adversely affect ESC
performance. Improperly inflated and
unevenly worn tires may also degrade
ESC performance. Any vehicle modifica-
tion or poor vehicle maintenance that
reduces the effectiveness of the ESC
system can increase the risk of loss of
vehicle control, vehicle rollover, personal
injury and death.
WARNING! (Continued)
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SAFETY
82
(Continued)
Full Off — If Equipped

The “Full Off” mode is intended for off-highway or
off-road use only and should not be used on any
public roadways. In this mode, TCS and ESC
features are turned off. To enter the “Full Off”
mode, push and hold the “ESC OFF” switch for
five seconds while the vehicle is stopped with the
engine running. After five seconds, a chime will
sound, the “ESC OFF Indicator Light” will illumi-
nate, and the “ESC OFF” message will display in
the instrument cluster. To turn ESC On again,
momentarily push the “ESC OFF” switch.
NOTE:
System may switch from ESC “Full Off” to
“Partial Off” mode when vehicle exceeds a
predetermined speed. When the vehicle
speed slows below the predetermined speed
the system will return to ESC “Full Off”.
ESC modes may also be affected by drive
modes (if equipped).
ESC Activation/Malfunction Indicator Light
And ESC OFF Indicator Light

The “ESC Activation/Malfunction
Indicator Light” in the instrument
cluster will come on when the igni
-
tion is turned to the “ESC On” mode.
It should go out with the engine running. If the
“ESC Activation/Malfunction Indicator Light”
comes on continuously with the engine
running, a malfunction has been detected in
the ESC system. If this light remains on after
several ignition cycles, and the vehicle has
been driven several miles (km) at speeds
greater than 30 mph (48 km/h), see an autho -
rized dealer as soon as possible to have the
problem diagnosed and corrected.

WARNING!

When in “Partial Off” mode, the TCS func -
tionality of ESC, (except for the limited slip
feature described in the TCS section), has
been disabled and the “ESC Off Indicator
Light” will be illuminated. When in
“Partial Off” mode, the engine power
reduction feature of TCS is disabled, and
the enhanced vehicle stability offered by
the ESC system is reduced.

Trailer Sway control (TSC) is disabled
when the ESC system is in the “Partial
Off” mode.
WARNING!
In the ESC “Full Off” mode, the engine
torque reduction and stability features
are disabled. Therefore, enhanced
vehicle stability offered by the ESC
system is unavailable. In an emergency
evasive maneuver, the ESC system will
not engage to assist in maintaining
stability. ESC “Full Off” mode is
intended for off-highway or off-road use
only.
The Electronic Stability Control (ESC)
cannot prevent the natural laws of
physics from acting on the vehicle, nor
can it increase the traction afforded by
prevailing road conditions. ESC cannot
prevent all accidents, including those
resulting from excessive speed in turns,
driving on very slippery surfaces, or
hydroplaning. ESC also cannot prevent
collisions.
WARNING! (Continued)
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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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SAFETY
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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