ECU LEXUS UX250H 2019 Repair Manual

3716-3. Do-it-yourself maintenance
6
Maintenance and care
Type ANormal fuse
Blown fuse
Type BNormal fuse
Blown fuse
Type CNormal fuse
Blown fuse
Type DNormal fuse
Blown fuse
■After a fuse is replaced
●When installing the lid, make sure that the
tab is installed securely.
●If the lights do not turn on even after the
fuse has been replaced, a bulb may need
replacement. ( P.374)
●If the replaced fuse blows again, have the
vehicle inspected by your Lexus dealer.
■If there is an overload in a circuit
The fuses are designed to blow, protecting
the wiring harness from damage.
■When replacing light bulbs
Lexus recommends that you use genuine
Lexus products designed for this vehicle.
Because certain bulbs are connected to cir-
cuits designed to prevent overload, non-
genuine parts or parts not designed for this
vehicle may be unusable.
A
B
A
B
A
B
WARNING
■To prevent system breakdowns and
vehicle fire
Observe the following precautions.
Failure to do so may cause damage to
the vehicle, and possibly a fire or injury.
●Never use a fuse of a higher amperage
rating than that indicated, or use any
other object in place of a fuse.
A
B

3756-3. Do-it-yourself maintenance
6
Maintenance and care
■Front turn signal lights (vehicles
with single-beam headlights)
1
Turn the bulb base counterclock-
wise.
2
Remove the light bulb.
3
When installing, reverse the steps
listed.
Replacing light bulb
WARNING
■Replacing light bulb
●Turn off the light. Do not attempt to
replace the bulb immediately after
turning off the light.
The bulb become very hot and may
cause burns.
●Do not touch the glass portion of the
light bulb with bare hands. When it is
unavoidable to hold the glass portion,
use and hold with a clean dry cloth to
avoid getting moisture and oils on the
bulb.
Also, if the bulb is scratched or
dropped, it may blow out or crack.
●Fully install light bulb and any parts
used to secure it. Failure to do so may
result in heat damage, fire, or water
entering the light unit. This may dam-
age the light or cause condensation to
build up on the lens.
■To prevent damage or fire
●Make sure bulb is fully seated and
locked.
●Check the wattage of the bulb before
installing to prevent heat damage.

3787-1. Essential information
7-1.Essential information
Press the switch.
All the turn signal lights will flash. To turn
them off, press the switch once again.
■Emergency flashers
●If the emergency flashers are used for a
long time while the hybrid system is not
operating (while the “READY” indicator
is not illuminated), the 12-volt battery may
discharge.
●If any of the SRS airbags deploy (inflate)
or in the event of a strong rear impact, the
emergency flashers will turn on automati-
cally. The emergency flashers will turn off
automatically after operating for approxi-
mately 20 minutes. To manually turn the
emergency flashers off, press the switch
twice. (The emergency flashers may not
turn on automatically depending on the
force of the impact and conditions of the
collision.)
1 Steadily step on the brake pedal
with both feet and firmly depress it.
Do not pump the brake pedal repeatedly
as this will increase the effort required to
slow the vehicle.
2Shift the shift lever to N.
If the shift lever is shifted to N
3 After slowing down, stop the vehi-
cle in a safe place by the road.
4 Stop the hybrid system.
If the shift lever cannot be shifted to
N
3 Keep depressing the brake pedal
with both feet to reduce vehicle
speed as much as possible.
4 To stop the hybrid system, press
and hold the power switch for 2
consecutive seconds or more, or
Emergency flashers
The emergency flashers are used to
warn other drivers when the vehicle
has to be stopped in the road due to
a breakdown, etc.
Operating instructions
If your vehicle has to be
stopped in an emergency
Only in an emergency, such as if it
becomes impossible to stop the
vehicle in the normal way, stop the
vehicle using the following proce-
dure:
Stopping the vehicle

3827-2. Steps to take in an emergency
The following may indicate a problem
with your hybrid transmission. Contact
your Lexus dealer or commercial tow-
ing service before towing.
The hybrid warning message shows
on the multi-information display and
the vehicle does not move.
 The vehicle makes an abnormal
sound.
Do not tow with a sling-type truck to
prevent body damage.
WARNING
■While towing
●When towing using cables or chains,
avoid sudden starts, etc. which place
excessive stress on the towing eyelets,
cables or chains. The towing eyelets,
cables or chains may become dam-
aged, broken debris may hit people,
and cause serious damage.
●Do not turn the power switch off.
There is a possibility that the steering
wheel is locked and cannot be oper-
ated.
■Installing towing eyelets to the vehi-
cle
Make sure that towing eyelets are
installed securely.
If not securely installed, towing eyelets
may come loose during towing.
NOTICE
■To prevent damage to the vehicle
when towing using a wheel-lift type
truck
●Do not tow the vehicle from the rear
when the power switch is OFF. The
steering lock mechanism is not strong
enough to hold the front wheels
straight.
●When raising the vehicle, ensure ade-
quate ground clearance for towing at
the opposite end of the raised vehicle.
Without adequate clearance, the vehi-
cle could be damaged while being
towed.
■To prevent damage to the vehicle
when towing with a sling-type truck
Do not tow with a sling-type truck, either
from the front or rear.
■To prevent damage to the vehicle
during emergency towing
Do not secure cables or chains to the
suspension components.
■Recreational towing (behind motor
home, etc.) (AWD models)
Never dinghy tow your vehicle to pre-
vent causing serious damage to the Elec-
tronic On-Demand AWD system and
transmission. ( P.161)
Situations when it is necessary to
contact dealers before towing
Towing with a sling-type truck

3837-2. Steps to take in an emergency
7
When trouble arises
From the front (2WD models)
Release the parking brake.
From the front (AWD models)
Use a towing dolly under the rear
wheels.
From the rear
Use a towing dolly under the front
wheels. If your vehicle is transported by a flat-
bed truck, it should be tied down at the
locations shown in the illustration.
If you use chains or cables to tie down
your vehicle, the angles shaded in
black must be 45°.
Do not overly tighten the tie downs or
the vehicle may be damaged.
If a tow truck is not available in an
emergency, your vehicle may be tem-
porarily towed using cables or chains
secured to the emergency towing eye-
lets. This should only be attempted on
hard surfaced roads for short distance
at under 18 mph (30 km/h).
A driver must be in the vehicle to steer
and operate the brakes. The vehicle’s
Towing with a wheel-lift type
truckUsing a flatbed truck
Emergency towing

3847-2. Steps to take in an emergency
wheels, drivetrain, axles, steering and
brakes must be in good condition.
To have your vehicle towed by another
vehicle, the towing eyelet must be
installed to your vehicle. Install the tow-
ing eyelet by following the specified
procedure.
1 Take out the towing eyelet.
(P.296)
2 Remove the eyelet cover using a
flathead screwdriver.
To protect the bodywork, place a rag
between the screwdriver and the vehicle
body as shown in the illustration.
3Insert the towing eyelet into the
hole and tighten partially by hand.
4 Tighten down the towing eyelet
securely using a wheel nut wrench
*
or hard metal bar.
*: If a wheel nut wrench is not equipped, a wheel nut wrench can be purchased at
your Lexus dealer.
5 Securely attach cables or chains to
the towing eyelet.
Take care not to damage the vehicle body.
6Enter the vehicle being towed and
start the hybrid system.
If the hybrid system does not start, turn the
power switch to ON.
7Shift the shift lever to N and release
the parking brake.
When the shift lever cannot be shifted:
P.168
■While towing
If the hybrid system is off, the power assist
for the brakes and steering will not function,
marking steering and braking more difficult.
■Wheel nut wrench
Vehicles with wheel nut wrench: Wheel nut
wrench is installed in luggage compart-
ment. ( P.296)
Vehicles without wheel nut wrench: Wheel
nut wrench can be purchased at your Lexus
dealer.
Emergency towing procedure

3937-2. Steps to take in an emergency
7
When trouble arises
bag sensor assembly, front impact sensors,
side impact sensors (front door), side
impact sensors (front), side impact sensors
(rear), driver’s seat position sensor, driver’s
seat belt buckle switch, front passenger
occupant classification system (ECU and
sensors), rear seat belt buckle switches (if
equipped), “AIR BAG ON” indicator light,
“AIR BAG OFF” indicator light, front pas-
senger’s seat belt buckle switch, seat belt
pretensioners, airbags, interconnecting wir-
ing and power sources. (P.31)
■Electric power steering system warning
light (warning buzzer)
When the 12-volt battery charge becomes
insufficient or the voltage temporarily
drops, the electric po wer steering system
warning light may come on and the warning
buzzer may sound.
■When the tire pressure warning light
comes on
Inspect the tires to check if a tire is punc-
tured.
If a tire is punctured: P.399
If none of the tires are punctured:
Turn the power switch off then turn it to ON.
Check if the tire pressure warning light
comes on or blinks.
If the tire pressure warning light blinks for
approximately 1 minute then stays on
There may be a malfunction in the tire pres-
sure warning system. Have the vehicle
inspected by your Lexus dealer immedi-
ately.
If the tire pressure warning light comes
on
1
After the temperature of the tires has
lowered sufficiently, check the inflation
pressure of each tire and adjust them to
the specified level.
2
If the warning light does not turn off
even after several minutes have
elapsed, check that the inflation pres-
sure of each tire is at the specified level
and perform initialization. ( P.351)
■The tire pressure warning light may
come on due to natural causes
The tire pressure warning light may come
on due to natural causes such as natural air leaks and tire inflation pressure changes
caused by temperature. In this case, adjust-
ing the tire inflation pressure will turn off the
warning light (after a few minutes).
■Conditions that the tire pressure warn-
ing system may not function properly
 P.348
WARNING
■If both the ABS and the brake system
warning lights remain on
Stop your vehicle in a safe place immedi-
ately and contact your Lexus dealer.
The vehicle will become extremely
unstable during braking, and the ABS
system may fail, which could cause an
accident resulting in death or serious
injury.
■When the electric power steering
system warning light comes on
When the light comes on yellow, the
assist to the power st eering is restricted.
When the light comes on red, the assist
to the power steering is lost and handling
operations of the steering wheel become
extremely heavy.
When steering wheel operations are
heavier than usual, grip the steering
wheel firmly and operate it using more
force than usual.
■If the tire pressure warning light
comes on
Be sure to observe the following precau-
tions.
Failure to do so could cause a loss of
vehicle control and result in death or
serious injury.
●Decelerate to the lowest appropriate
speed as soon as possible. Do not
drive over 50 mph (80 km/h).
●Check and adjust the tire inflation
pressure immediately.

4087-2. Steps to take in an emergency
■Starting the hybrid system when the 12-
volt battery is discharged
The hybrid system cannot be started by
push-starting.
■To prevent 12-volt battery discharge
●Turn off the headlight s, the air condition-
ing system, the audio system, etc. while
the hybrid system is off.
●Turn off any unnecessary electrical com-
ponents when the vehicle is running at a
low speed for an extended period, such
as in heavy traffic.
■Charging the 12-volt battery
The electricity stored in the 12-volt battery
will discharge gradua lly even when the
vehicle is not in use, due to natural dis-
charge and the draining effects of certain
electrical appliances. If the vehicle is left for
a long time, the 12-volt battery may dis-
charge, and the hybrid system may be
unable to start. (The 12-volt battery
recharges automatically while the hybrid
system is operating.)
■When the 12-volt battery is removed or
discharged
●Information stored in the ECU is cleared.
When the 12-volt battery is depleted,
have the vehicle inspected at your Lexus
dealer.
●In some cases, it may not be possible to
unlock the doors using the smart access
system with push-button start when the
12-volt battery is discharged. Use the
wireless remote control or the mechani-
cal key to lock or unlock the doors.
●The hybrid system may not start on the
first attempt after the 12-volt battery has
recharged but will start normally after the
second attempt. This is not a malfunction.
●The power switch mode is memorized by
the vehicle. When the 12-volt battery is
reconnected, the system will return to the
mode it was in before the 12-volt battery
was discharged. Before disconnecting
the 12-volt battery, turn the power switch
off.
If you are unsure what mode the power
switch was in before the 12-volt battery discharged, be especially careful when
reconnecting the 12-volt battery.
●The power back door must be initialized.
(
 P.119)
■When replacing the 12-volt battery
●Use a Central Degassing type 12-volt
battery (European Regulations).
●Use a 12-volt battery that the case size is
same as the previous one (LN1), 20 hour
rate capacity (20HR) is equivalent
(45Ah) or greater, and performance rat-
ing (CCA) is equivalent (286A) or
greater.
• If the sizes differ, the 12-volt battery can- not be properly secured.
• If an improper 12-volt battery is used, bat-
tery performance may decrease and the
hybrid system may not be able to restart.
• If the 20 hour rate capacity is low, even if
the time period where the vehicle is not
used is a short time, the 12-volt battery
may discharge and hybrid system may
not be able to start.
●Use a 12-volt battery with a handle. If a
12-volt battery without a handle is used,
removal is more difficult.
●After exchanging, firmly attach the fol-
lowing items to the exhaust hole of the 12-
volt battery.
• Confirm that the elbow is securely attached to the exhaust hose and exhaust
hole.
• Confirm that the exhaust hole plug is securely attached to the exhaust hole that
the elbow is not attached to.
• Use the elbow/exhaust hole plug included with the 12-volt battery
exchanged or the on e installed on the
battery prior to the exchange. (Depend-
ing on the 12-volt battery to be
exchanged, the exhaust hole may be
plugged.)

4107-2. Steps to take in an emergency
If the engine coolant temperature
gauge enters the red zone or
“Engine Coolant Temp High Stop in
a Safe Place See Owner’s Manual”
is shown on the multi-information
display
1
Stop the vehicle in a safe place and
turn off the air conditioning system,
and then stop the hybrid system.
2
If you see steam:
Carefully lift the hood after the
steam subsides.
If you do not see steam:
Carefully lift the hood.
3
After the hybrid system has cooled
down sufficiently, inspect the hoses
WARNING
■When replacing the 12-volt battery
●When the vent plug is close to the hold
down clamp, the battery fluid (acid)
may leak.
●For information regarding battery
replacement, contact your Lexus
dealer.
●After exchanging, securely attach the
elbow connected to the exhaust hose,
and exhaust hole plug to the exhaust
hole of the exchanged 12-volt battery.
If not properly installed, gases (hydro-
gen) may leak into the vehicle interior,
and there is the possible danger of the
gas igniting and exploding.
NOTICE
■When handling jumper cables
When connecting the jumper cables,
ensure that they do not become entan-
gled in the cooling fans or belt.
■To prevent damaging the vehicle
The exclusive jump starting terminal is to
be used when charging the 12-volt bat-
tery from another vehicle in an emer-
gency. It cannot be used to jump start
another vehicle.
If your vehicle overheats
The following may indicate that
your vehicle is overheating.
 The engine coolant temperature
gauge ( P.78, 82) enters the
red zone, or a loss of hybrid sys-
tem power is experienced. (For
example, the vehicle speed does
not increase.)
 “Engine Coolant Temp High Stop
in a Safe Place See Owner’s
Manual” or “Hybrid system over-
heated Output power reduced” is
shown on the multi-information
display.
 Steam comes out from under the
hood.
Correction procedures

4328-1. Specifications
*:Table 1  Occupant loading and distribution for vehicle normal load for various desig-
nated seating capacities
Pneumatic tire
A mechanical device made of rubber, chemicals, fabric and
steel or other materials, that, when mounted on an automo-
tive wheel, provides the traction and contains the gas or fluid
that sustains the load
Radial ply tire
A pneumatic tire in which the ply cords that extend to the
beads are laid at substantiall y 90 degrees to the centerline
of the tread
Reinforced tireA tire designed to operate at higher loads and at higher
inflation pressures than the corresponding standard tire
Section width
The linear distance between the exteriors of the sidewalls of
an inflated tire, excluding elevations due to labeling, decora-
tion, or protective bands
SidewallThat portion of a tire between the tread and bead
Sidewall separationThe parting of the rubber comp ound from the cord material
in the sidewall
Snow tire
A tire that attains a traction index equal to or greater than
110, compared to the ASTM E-1136 Standard Reference
Test Tire, when using the snow traction test as described in
ASTM F-1805-00, Standard Test Method for Single Wheel
Driving Traction in a Straight Line on Snow-and Ice-Cov-
ered Surfaces, and which is ma rked with an Alpine Symbol
( ) on at least one sidewall
Test rimThe rim on which a tire is fitt ed for testing, and may be any
rim listed as appropriate for use with that tire
TreadThat portion of a tire that comes into contact with the road
Tread ribA tread section running circ umferentially around a tire
Tread separationPulling away of the tread from the tire carcass
Treadwear indicators (TWI)The projections within the principal grooves designed to
give a visual indication of the degrees of wear of the tread
Wheel-holding fixtureThe fixture used to hold the wheel and tire assembly
securely during testing
Tire related termMeaning