brakes VOLVO XC90 TWIN ENGINE 2018 Service Manual

HYBRID INFORMATION
406General information about Twin
Engine
Twin Engine vehicles are driven just like any
other vehicle, but certain functions differ from a
vehicle powered exclusively by gasoline. The
electric motor powers the vehicle primarily at low
speeds; the gasoline engine is used at higher
speeds or during more active driving. The instrument panel displays Twin Engine-spe-
cific information - charging information, selected
drive mode, distance to discharged battery and
hybrid battery charge level.
Different drive modes can be selected while driv-
ing, e.g. electric power only or, if more power is
needed, a combination of electric and gasoline
power. The vehicle calculates the optimal combi-
nation of driveability, driving experience, environ-
mental impact and fuel economy for the selected
drive mode.
In order to function optimally, the hybrid battery
(and its electrical drive systems) and the gasoline
engine (and its drive systems) must be at the
correct operating temperature. Battery capacity
can be considerably reduced if the battery is too
cold or too hot. Preconditioning prepares the
vehicle's drive systems and passenger compart-
ment before driving to help reduce both wear and
energy consumption. It also helps increase the
hybrid battery's range.
The hybrid battery, which powers the electric
motor, is recharged using the charging cable. It
can also be recharged during light braking and through engine braking in gear position B. The
combustion engine can also help recharge the
hybrid battery.
Important
No electrical current
Keep in mind that if there is no electrical current
to the vehicle, i.e. the ignition is switched off or
the start battery is discharged, certain functions
such as brakes, power steering, etc. will not work.
WARNING If the vehicle does not have electrical current
and both the electric motor and the gasoline
engine are switched off, the brakes cannot be
used to stop the vehicle.
Towing not permitted
Never tow a Twin Engine vehicle behind another
vehicle, as this could damage the electric motor.
Exterior engine noise
WARNING
Keep in mind that the vehicle does not emit
any engine noise when using the electric
motor and may therefore be difficult to detect
for children, pedestrians, cyclists or animals.
This is especially true at low speeds, e.g. in
parking lots.
High-voltage electrical current
WARNING Several components in the vehicle work with
high voltage that can be hazardous in case of
an incorrect procedure. These components
and any orange wiring in the vehicle may only
be handled by trained and qualified Volvo
service technicians.
Do not touch anything that is not clearly descri-
bed in this Owner's Manual.
Related information
• Charging the hybrid battery (p. 407)
• Hybrid gauge (p. 87)
• Drive modes (p. 445)
• Starting and stopping preconditioning
(p. 231)
• Hybrid battery (p. 619)
• Factors affecting electric motor range
(p. 458)
• Gear selector positions for automatic trans-
missions (p. 439)
• Towing using a towline (p. 476)

HYBRID INFORMATION
}}
407
Charging the hybrid battery
In addition to the conventional fuel tank, your
vehicle is also equipped with a rechargeable
lithium-ion hybrid battery.
The hybrid battery can be recharged using the
charging cable stored in a storage space in the
cargo compartment.
WARNING
The hybrid electrical system in your vehicle
uses high voltage electrical current. Any dam-
age to this system or to the hybrid battery
may result in the danger of overheating, fire,
or serious injury. If the vehicle is involved in a
collision or subjected to flooding, fire, etc.,
have it inspected by a trained and qualified
Volvo service technician. Prior to this inspec-
tion, the vehicle should be parked outdoors at
a safe distance from any building or poten-
tially flammable materials.
The hybrid battery's charging time depends on
the charging current used.
NOTE The capacity of the hybrid battery diminishes
somewhat with age and use, which could
result in increased use of the gasoline engine
and consequently, slightly higher fuel con-
sumption.
WARNING If the hybrid battery needs to be replaced, this
may only be done by Volvo retailer or author-
ized Volvo workshop.
Charging cable handle and charging socket.
Charging status is indicated in three ways:
• The indicator lights in the charging module
(the unit connected to the wall outlet).
• Indicator light in the vehicle's charging
socket.
• Images and text in the instrument panel.
The hybrid battery's charging process also
charges the vehicle's start battery.
If the hybrid battery's temperature is below
-10 ºC (14 ºF) or above 40 ºC (104 ºF), some of
the vehicle's functions may be reduced or not
available at all. The electric motor cannot be used if the battery's
temperature is too low or too high. If the PURE
drive mode is selected, the gasoline engine will
start.
Charging using the gasoline engine
The vehicle generates electrical current to charge the
battery, e.g. when the driver lightly presses the brake
pedal or when engine braking is used on downgrades.
The vehicle can also generate current to the
hybrid battery to charge it.
• The hybrid battery can also be recharged by
lightly depressing the brake pedal, i.e. during
light braking. This converts the vehicle's
kinetic energy to electrical energy, which is
used to charge the hybrid battery.
• In gear position B, the electric motor brakes
the vehicle when the accelerator pedal is

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429
Brake functions
The vehicle's brakes are used to reduce speed
or prevent the vehicle from rolling.
In addition to the wheel brakes and parking
brakes, the vehicle is also equipped with a num-
ber of automatic brake assist functions. These
systems help the driver by e.g. keeping the vehi-
cle stationary when the brake pedal is not
depressed (e.g. at a traffic light or intersection),
when starting up a hill or when driving down a hill.
Depending on how the vehicle is equipped, the
following brake assist functions may be included:
• Auto-hold brakes (Auto Hold)
• Hill Start Assist (Hill Start Assist)
• Braking assist after a collision
• City Safety
• Hill Descent Control (Hill Descent Control)
Related information
•Brakes (p. 429)
• Parking brake (p. 432)
• Auto-hold brakes (p. 436)
• Braking assist after a collision (p. 437)
• Hill Start Assist (p. 437)
• City Safety™ (p. 335)
• Hill Descent Control (p. 454) Brakes
The brake pedal is used to apply the vehicle's
regular brakes, which are part of the brake sys-
tem.
The vehicle is equipped with two brake circuits. If
one brake circuit is damaged, the brake pedal will
go down further when depressed. More pressure
will then be required from the driver for normal
braking effect.
WARNING
If the vehicle does not have electrical current
and both the electric motor and the gasoline
engine are switched off, the brakes cannot be
used to stop the vehicle.
In very hilly areas or when driving with a heavy
load, gear position B can be used to augment the
brakes with engine braking.
Use the Off Road drive mode to increase the
engine braking effect when driving on steep
downgrades at low speeds.
Anti-lock brakesThe vehicle is equipped with an Anti-lock Braking
System (ABS), which can help prevent the
wheels from locking and help maintain steering
control when braking. Vibrations may be felt from
the brake pedal when ABS is operating, which is
normal.
After the vehicle is started, a brief test of the
ABS system is automatically performed when the driver releases the brake pedal. An additional
automatic test of the system may be performed
when the vehicle is traveling at a low speed. Dur-
ing the test, the brake pedal may feel as though it
is pulsating.
Light braking charges the hybrid batteryWhen the brakes are applied lightly, the electric
motor braking function is used. This converts the
vehicle's kinetic energy into electrical energy,
which is used to charge the hybrid battery. When
the battery is being charged with the electric
motor braking function, this will be indicated in
the instrument panel.
When the battery is being charged with the electric
motor braking function, this will be indicated in the
instrument panel.
This function is active at speeds in the range of
150-5 km/h (93-3 mph). When braking at
speeds outside of this range, or during harder
braking, the hydraulic braking system is used to

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430
augment braking. This is indicated in the instru-
ment panel with the pointer down in the red area.
Symbols in the instrument panel
Symbol
Meaning A
B
Check the brake fluid level. If the
level is low, fill brake fluid and
check to determine the reason for
the loss of brake fluid. A
B
Fault in pedal sensor. Symbol
Meaning A
B
Steady glow for 2 seconds after
the engine is started: Automatic
function check.
Steady glow for more than 2 sec-
onds: Fault in the ABS system. The
vehicle's regular brake system is
still working, but without the ABS
function. If the message Brake pedal Cha-
racteristics changed Service
required is displayed, the "Brake-
by-wire" system is not functioning
properly. The brake pedal will go
down further than normal and
greater pressure will be needed on
the pedal to achieve braking effect. A
Canadian models.
B US models.
WARNING •
If both symbols illuminate at the same
time and the brake level is below the MIN
mark in the reservoir or if a brake system-
related message is shown in the instru-
ment panel: DO NOT DRIVE. Have the
vehicle towed to a trained and qualified
Volvo service technician and have the
brake system inspected.
• If both symbols illuminate at the same
time and the brake level is normal (not
below the MIN mark in the reservoir) or if
a brake system-related message is
shown in the instrument panel: drive the
vehicle carefully to an authorized Volvo
workshop and have the brake system
inspected by a trained and qualified Volvo
service technician.
Related information
• Brake Assist System (p. 431)
• Auto-hold brakes (p. 436)
• Hill Start Assist (p. 437)
• Braking on wet roads (p. 431)
• Braking on salted roads (p. 431)
• Maintenance of the brake system (p. 432)
• Brake lights (p. 160)

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431
Brake Assist System
The brake enhancing system, Brake Assist
System (BAS

), helps increase braking force and
thereby reduce braking distance. The system monitors the driver's braking habits
and increases braking force when necessary.
Braking force can be increased up to the point at
which the ABS intervenes. The function is deacti-
vated when pressure on the brake pedal is
decreased.
Related information
• Brakes (p. 429) Braking on wet roads
Prolonged driving in heavy rain without braking
may cause braking effect to be slightly delayed
the first time the brakes are applied.
This may also occur after washing the vehicle. It
will then be necessary to apply greater pressure
to the brake pedal. You should therefore maintain
a greater distance to the vehicle ahead.
Firmly apply the brakes after washing the vehicle
or driving on wet roads. This helps warm up the
brake discs, enabling them to dry more quickly
and protecting them against corrosion. Consider
the current traffic situation when braking.
Related information
• Brakes (p. 429)
• Braking on salted roads (p. 431) Braking on salted roads
When driving on salted roads, a layer of salt may
form on the brake discs and brake pads.
This could increase stopping distance. Maintain
an extra large safety distance to the vehicle
ahead. Make sure to also:
• Apply the brakes from time to time to help
remove salt. Make sure braking does not
pose a risk to any other road users.
• Gently apply the brakes when you have fin-
ished driving and before driving again.
Related information
•Brakes (p. 429)
• Braking on wet roads (p. 431)

STARTING AND DRIVING
432Maintenance of the brake system
Regularly check the brake system components
for wear. To keep the vehicle as safe and reliable as possi-
ble, follow the Volvo service schedule specified in
the Warranty and Maintenance Records Informa-
tion booklet. New and replaced brake pads and
brake discs do not provide optimal braking effect
until they are "broken in" by driving a few hun-
dred kilometers (miles). Compensate for the
reduced braking effect by applying greater pres-
sure to the brake pedal. Volvo recommends only
using brake pads approved for your Volvo.
CAUTION The brake system's components should be
regularly checked for wear.
Contact a workshop for advice on how to do
this or let a workshop perform the inspection
- an authorized Volvo workshop is recom-
mended.
Related information
•
Brakes (p. 429) Parking brake
The parking brake helps keep the vehicle sta-
tionary by mechanically locking two wheels.
The parking brake controls are located in the tunnel
console between the seats.
When the electric parking brake is being applied,
a faint sound can be heard from the brake's elec-
tric motor. This sound can also be heard during
the automatic function check of the parking
brake.
If the vehicle is stationary when the parking brake
is applied, it will only be applied to the rear
wheels. If it is applied while the vehicle is moving,
the normal brakes will be used on all four wheels.
Braking will be transferred to only the rear
wheels when the vehicle is almost stopped.
Related information
• Activating and deactivating the parking brake
(p. 433)
• Parking on a hill (p. 434)
• Parking brake malfunction (p. 435)
• Auto-hold brakes (p. 436)

STARTING AND DRIVING
436Auto-hold brakes
With the Auto-hold brake function, the driver can
release the brake pedal and the brakes will
remain applied, for example, when the vehicle
has stopped at a traffic light or intersection.
When the vehicle stops, the brakes are activated
automatically. The function can use either the
normal brakes or the parking brakes to keep the
vehicle stationary and works on flat surfaces or
hills. When driving off, the brakes will be automat-
ically released if the driver's seat belt is buckled.
NOTE When braking to a stop on an uphill or down-
hill gradient, depress the brake pedal with
slightly more force than usual before releas-
ing to ensure that the vehicle cannot move at
all.
The parking brake is activated if:
•
the vehicle is switched off
• the driver's door is opened
• the driver's seat belt is removed
• the vehicle has been stationary for a pro-
longed period of time (5-10 minutes)
Symbols in the instrument panel Symbol
Meaning This symbol illuminates when the
function is using the normal brakes
to keep the vehicle stationary.
A
B
This symbol illuminates when the
function is using the parking brake
to keep the vehicle stationary. A
Canadian models.
B US models.
Related information
• Activating and deactivating Auto-hold at a
standstill (p. 436)
• Brakes (p. 429)
• Parking brake (p. 432)
• Hill Start Assist (p. 437) Activating and deactivating Auto-
hold at a standstill
The Auto-hold brake function at a standstill is
activated with the button in the tunnel console.
–
Press the button in the tunnel console to
activate or deactivate the function.
>

The indicator light in the button will illumi-
nate when the function is activated. The
function will remain active the next time
the vehicle is started.

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437
When shutting offIf the function is active and holding the
vehicle stationary using the normal
brakes (A symbol lit), the brake pedal
must be depressed while pressing the
button in order to deactivate Auto-hold. •
The function will remain off until it is reactiva-
ted.
• When Auto-hold is switched off, Hill Start
Assist (HSA) will remain active to help pre-
vent the vehicle from rolling backward when
starting up a hill.
Related information
•Auto-hold brakes (p. 436) Hill Start Assist
The function for assisting when starting the vehi-
cle on inclines, Hill Start Assist (HSA), helps
prevent the vehicle from rolling backward when
starting on an uphill gradient. When backing up
a hill, HSA helps prevent the vehicle from rolling
forward.
The function retains pressure from the brake
pedal in the brake system for several seconds
after the brake pedal has been released.
This temporary braking effect is released after a
few seconds or when the driver begins driving.
Hill Start Assist is available even if the Auto-hold
brake function is switched off.
Related information
• Auto-hold brakes (p. 436)
• Brakes (p. 429) Braking assist after a collision
In a collision in which the activation level is
reached for the pyrotechnic seat belt tensioners
or airbags, or if a collision with a large animal is
detected, the vehicle's brakes will be automati-
cally activated. This function is intended to help
prevent or reduce the effects of any subsequent
collision.
After a serious collision, it may no longer be pos-
sible to control and steer the vehicle. In order to
avoid or mitigate a possible further collision with
a vehicle or an object in the vehicle's path, the
brake assist system is activated automatically to
help stop the vehicle safely.
The brake lights and hazard warning flashers are
activated during braking. When the vehicle has
stopped, the hazard warning flashers will con-
tinue to flash and the parking brake will be
applied.
If braking is not appropriate, e.g. if there is a risk
of being hit by passing traffic, the driver can over-
ride the system by depressing the accelerator
pedal.
This function assumes that the brake system is
intact after a collision.
Brake assist is part of the Rear Collision Warning
and Blind Spot Information safety systems.

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* Option/accessory. 445
Drive modes
Drive modes affect the vehicle's driving charac-
teristics in different ways to enhance and sim-
plify the driving experience in certain types of sit-
uations. Drive modes enable easy access to the vehicle's
many functions and settings in different driving
situations. The following systems are adapted to
help optimize driving characteristics in each drive
mode:
• Steering
• Engine/transmission/all-wheel drive
• Brakes
• Pneumatic suspension* and shock absorbers
• Instrument panel
• Climate control settings
Select the drive mode that is best suited to the
current driving conditions. Keep in mind that not
all drive modes are available in all situations.
Available drive modes
WARNING Keep in mind that the vehicle does not emit
any engine noise when using the electric
motor and may therefore be difficult to detect
for children, pedestrians, cyclists or animals.
This is particularly true at low speeds, e.g. in
parking lots.
WARNING
Do not leave the vehicle in an unventilated
area with a drive mode activated and the com-
bustion engine switched off. The engine will
start automatically if the charge level in the
hybrid battery is low and the resulting exhaust
gases can be very harmful to people and ani-
mals.
HYBRID
•
This is the default mode in which the electric
motor and combustion engine work together.
The vehicle starts in Hybrid mode. The control
system uses both the electric motor and the gas-
oline engine - separately or in tandem - and cal-
culates optimal utilization with regard to perform-
ance, fuel consumption and comfort. At high
speeds, ground clearance is automatically low-
ered 4
to reduce air resistance. Driving capacity on
the electric motor alone is determined by factors such as the hybrid battery's charge level, the
need for heat/cooling in the passenger compart-
ment, etc.
If there is sufficient charge in the battery, it is
possible to drive solely on electric power. When
the accelerator pedal is pressed, only the electric
motor will be activated until the battery reaches a
certain charge level. Above this level, the current
in the battery cannot supply the power requested
by the accelerator pedal and the combustion
engine will start.
When the hybrid battery's charge level is low, the
combustion engine will start more frequently to
save the remaining current in the battery. Charge
the hybrid battery from a 120-240 volt outlet
using a charging cable, or activate
Charge in
Function view to reset the option of only using
the electric motor.
This drive mode is designed for low energy con-
sumption with an optimized mix between the
electric motor and gasoline engine, without com-
promising on climate comfort or driving experi-
ence. When faster acceleration is requested by
the driver, the electric driveline will be utilized to
help provide maximum additional power. The
vehicle also monitors the driving conditions and
automatically engages all-wheel drive if neces-
sary. All-wheel drive and extra electric power are
always available regardless of the battery's
charging status. 4
For vehicles with pneumatic suspension.

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454
NOTE
When LSC with HDC is activated in the OFF
ROAD drive mode, the feel of the accelerator
pedal and engine response will change.
NOTE
This drive mode is not designed to be used
for normal street driving.
NOTE
The function is deactivated when driving at
high speeds and must be reactivated at lower
speeds if so desired.
Related information
•
Activating and deactivating Low Speed Con-
trol using the function button (p. 454)
• Changing drive mode (p. 449)
• Hill Descent Control (p. 454)
• All Wheel Drive (AWD) (p. 443) Activating and deactivating Low
Speed Control using the function
button
Vehicles that are not equipped with drive mode
controls in the tunnel console have a function
button for Low Speed Control with Hill Descent
Control in the center display's Function view.
Selecting Low Speed Control in the
center display's Function view
– Tap the Hill Descent Control button to
activate or deactivate the function. > An indicator light in the button will illumi-
nate when the function is activated.
When the engine is switched off, the function will
be automatically deactivated.
NOTE The function is deactivated when driving at
high speeds and must be reactivated at lower
speeds if so desired.
Related information
•
Low Speed Control (p. 453)
• Changing drive mode (p. 449) Hill Descent Control
The function for assisting when driving downhill,
Hill Descent Control (HDC), is a low-speed
function with increased engine braking. The
function makes it possible to increase or
decrease the vehicle's speed on steep downhill
gradients by only using the accelerator pedal,
without applying the brakes.
The function is included in the Off Road drive
mode.
HDC is designed for driving on rough roads at
low speeds and downhill gradients with slippery
or otherwise difficult road surfaces. The driver
does not need to use the brake pedal but can
instead focus on steering.
WARNING
HDC is only intended to be a supplementary
braking aid and it does not function in all sit-
uations.
The driver is always ultimately responsible for
operating the vehicle in a safe manner.
FunctionHill Descent Control allows the vehicle to move
forward or backward at very low speeds assisted
by the brake system. The driver can increase the
speed by pressing the accelerator pedal. When
the accelerator pedal is released, the vehicle will
return to very low speed regardless of how steep