2001 TOYOTA PRIUS warning light

BODY ELECTRICAL ± MULTIPLEX COMMUNICATION SYSTEM 142
SYSTEM OPERATION
1. General
The ECUs that pertain to the body electrical system perform the functions and system controls described be-
low.
Gateway ECU
Conversion of data between AVC-LAN and BEAN
Transmission of vehicle information to the display ECU, in order for it to be displayed on multi-informa-
tion display
Body ECU
Power window system control (Front, Rear passenger only)
Door lock control system control
Wireless door lock remote control system control
Theft deferrent system control
Daytime running light system control
Illuminated entry system control
Light auto turn-off system control
Seat belt warning system control
Key reminder system control
Diagnosis
Meter ECU
Meter control
Illumination and flashing control of indicator and warning lights
Sounding control of warning buzzer
Air Conditioning ECU
Air Conditioning control
ECM
Engine control
Diagnosis
Display ECU
Transmission and reception associated with audio and visual functions

BODY ELECTRICAL ± METER
182BE04
182BE16
U.S.A. Model
Canada Model Master Warning LightOutput Control
Warning Light
ªREADYº Light 146
METER
COMBINATION METER
1. General

The combination meter is available as a digital display type. It is located at the upper center of the instru-
ment panel to improve its visibility.

For this combination meter, a meter ECU that effects multiplex communication through the use of BEAN
(Body Electronics Area Network) has been adopted.

The display of the speedometer can be switched between km / h and MPH readings by operating the km / h-
MPH selector switch located in the middle of the center cluster. Furthermore, the odo / trip meter can be
switched between odometer and tripmeter readings by operating the odo / trip selector / reset switch located
in the middle of the center cluster.

A ªREADYº light that informs the driver that the vehicle is ready to be driven has been adopted.

A master warning light that informs the driver if an abnormality occurs in either the EMPS (Electric Motor-
assisted Power Steering), HV batteries, or the THS (TOYOTA Hybrid System) has been adopted.

An output control warning light has been adopted to show the drop of power function due to the output
drop of HV batteries.

For the purpose of making corrections in the calculation of the fuel level by the meter ECU, two inclination
sensors that detect the vehicle's longitudinal and latitudinal inclinations have been provided in the meter
ECU. In addition, an outer ambient temperature sensor has been provided in the fuel tank to detect the
temperature in the fuel tank.

BODY ELECTRICAL ± METER
182BE08
Flashes when the
ignition switch is
turned to START
Illuminates when
the vehicle is ready
to be driven
Service Tip

Inverter unit cover is left open.

HV ECU has detected a collision.149
ªREADYº Light
When the shift position is P, turning the ignition
switch to START causes the ªREADYº light to
flash and enables the vehicle to be driven. Then,
this indicator illuminates and the buzzer sounds
simultaneously.
If the indicator does not illuminate, the vehicle cannot be driven because one of the driving prohibition
conditions listed below applies.

Service plug disconnected.

Hybrid system abnormality.

Driving prohibition condition due to overload
on MG1, MG2 or inverter.
Master Warning Light
A master warning light that informs the driver if an abnormality occurs in either the EMPS, HV batteries,
or the THS has been adopted.
If an abnormality occurs in the system, the master warning light illuminates and the multi-information dis-
play shows the warning items. For details, see page 178.
Output Control Warning Light
An output control warning light has been adopted to show the drop of power function due to the output drop
of HV batteries.
This warning light comes on when the temperature of HV batteries is higher or lower than that of specified
range, or when SOC (State of Charge) is lower than the specified value with the shift position in R range.
When this warning light comes on, avoid sudden acceleration and drive carefully.

BODY ELECTRICAL ± ACCESSORIES
182BE38
EMPS System
Abnormality WarningTHS Abnormality
Warning
HV Battery Warning
182BE39
178
3) Interrupt Screen
a. General
If an abnormal condition occurs in the ve-
hicle system, even if another screen is being
displayed, the interrupt screen automatically
indicates a warning to inform the driver of an
abnormality in the system. The warning in-
dication screen flashes for 5 seconds the
mark of the system in which the abnormality
occurred. Then, it illuminates and remains
displayed until the screen is switched or the
system is reinstated to normal.

List of Warning Display Items 
Warning Display ItemDescription of Warning
EMPS System
Abnormality WarningWhen an abnormality occurs in the EMPS (Electric Motor-assisted
Power Steering) system.
HV Battery Warning*When the HV battery voltage drops.
THS Abnormality
WarningWhen an abnormality occurs in the THS (TOYOTA Hybrid System).
*: While ªREADYº light is lighting.
b. HV Battery Warning
When starting THS (when turning the IG key to START position) and if HV battery is displayed in this
interrupt screen, it means that HV battery has abnormality.
4) On-screen
If the screen switches to another screen while
displaying a warning indication, the mark of
the system in which the abnormality occurred
is displayed at the top right area of the screen.
The displayed mark disappears when the sys-
tem is reinstated to normal.

BODY ELECTRICAL ± ACCESSORIES
182BE41
RRP DBody
ECUUARTPower
Window
Master
SwitchDoor Control
Switch (Manual)
Door Control
Switch (Key-linked)
169BE10
Key Unlock
Warning SwitchDoor Courtesy
Switch
Door Lock
MotorsBody
ECU
Serial Data Link
Wireless Door
Control Receiver
Horn
RelayHeadlight
RelayTaillight
RelayTransmitter183
DOOR LOCK CONTROL SYSTEM
The door lock control system has the following features:
This system has a ªkey-linked lock and unlockº, ªkey-confine preventionº and ªmanual unlock prohibi-
tionº functions.
A 2-step unlock function is provided to unlock the driver's door by turning the key cylinder first and to
unlock passenger's door by turning it the second time.
The control of this system is effected by the body ECU. The door lock control signal from the driver's door
is transmitted from the power window master switch to the body ECU through the UART (Universal
Asynchronous Receiver Transmitter).
If you unlock using the ignition key from the conditions in which all the doors are locked, the dome light
will be lighted.

System Diagram 
WIRELESS DOOR LOCK REMOTE CONTROL SYSTEM
The wireless door lock remote control system has the following features:
In this system, the wireless door control receiver performs the code identification process and the body
ECU effects the door lock control. Serial data link is provided for communication between the wireless
door control receiver and the body ECU.
A key-holder type transmitter has been adopted, and it contains the following three switches: the door lock
switch, door unlock switch, and panic switch.
A rolling code system, in which the signal configuration changes each time when a signal is transmitted
by the transmitter, has been adopted.
Panic alarm operation has been adopted.
The verification light function has been adopted. When the transmitter is used to lock or unlock the doors,
this function flashes the taillights to inform that the operation has been completed. However, at the time
of unlocking, the dome light will be lighted.

BODY ELECTRICAL ± ACCESSORIES
182BE44
SRS
Warning LightInflator and Bag
for Front Passenger
Front Airbag
Sensor (RH)
Side Airbag
Assembly (RH)
Seat Belt
Pretensioner (RH)
Side Airbag
Sensor (RH) Airbag Sensor
Assembly Seat Belt
Pretensioner (LH) Side Airbag
Sensor (LH) Side Airbag
Assembly (LH)Front Airbag
Sensor (LH)Inflator and Bag
for Driver
182BE45
CollisionImpact
Front Airbag Sensors
Airbag Sensor
Assembly
 Inflator
 (For Driver and Front Passenger)
 Seat Belt Pretensioner
 (LH and RH)
Inflator
(For Right Side or Left Side)
CollisionImpactSide
Airbag
Sensor 188
SRS AIRBAG AND SRS SIDE AIRBAG
The SRS (Supplemental Restraint System) airbags are provided for the driver and front passenger. The
SRS airbags have been designed to help reducing the shocks to the heads and chests of the driver and front
passenger in the event of a frontal impact collision as supplements to the seat belts.
This system is a 3-sensor type airbag system to detect the impact during a front collision using the airbag
sensor assemblies and front airbag sensor, and to make the airbag system and seat belt pretensioner operate
as well.
Also, the function of the ECU to memorize the seat belt wearing condition while inflating the airbag is
added.
The SRS side airbags are provided for the driver and front passenger as an option. The SRS side airbags
have been designed to help reducing the impact energy that is transmitted to the driver and front passenger
in the event of a side collision.
The driver side and the front passenger side are each provided with one sensor.
A fuel cut control has been adopted to stop the fuel pump when the SRS airbag is deployed, thus helping
reduce fuel leakage.

System Diagram 

BODY ELECTRICAL ± ACCESSORIES
182BE47 Warning
Buzzer
(Driver)
Seat Belt
Warning
Light
(Driver)Seat Belt
Warning Light
(Front Passenger Side)
Combination Meter
Seat Belt
Buckle
SwitchOccupant Detection
Sensor
Seat Belt Buckle
Switch
Driver
SideFront Passenger
Side
159BE19 159BE18
182BE53
Occupant Detection Sensor
Front Passenger Seat
Upside ViewSpacerElectrode Sheet
Electrode Sheet
Sensor OFF
Occupant
Sensor ON 190

SEAT BELT WARNING SYSTEM
1. General
A seat belt warning system has been adopted. If the driver's seat belt is not buckled, the warning light flashes
and the buzzer sounds. If the front passenger seat belt is not buckled, it flashes the warning light. When the
ignition switch is turned ON, this system determines whether or not the seat belt is buckled by the ON or OFF
condition of the switch that is provided in the seat belt buckle. The occupant detection sensor provided in
the seat cushion of the front passenger seat determines whether or not an occupant is seated in the front pas-
senger seat.
2. Occupant Detection Sensor
The occupant detection sensor, which is enclosed in the seat cushion of the front passenger seat, is used to
detect whether or not the front passenger seat is occupied.
This sensor, which is shaped as illustrated below, consists of a construction in which two sheets of electrodes
sandwich a spacer. When the occupant is seated, the electrode sheets come in contact with each other through
the hole that is provided in the spacer portion, thus enabling the current to flow.
Thus, the sensor detects whether or not an occupant is seated in the front passenger seat.

B04748
B04749
1. +Terminal
2. +Terminal3. ±Terminal
4. ±Terminal
B04750
± INTRODUCTIONFOR ALL OF VEHICLES
IN±13
13 Author: Date:
2001 PRIUS (RM778U)
2. PRECAUTIONS TO BE OBSERVED WHEN INSPECT-
ING OR SERVICING ENGINE COMPARTMENT
The PRIUS, automatically turns the engine ON and OFF when
the ignition switch is set to the ON position provided that the
READY light on the instrument panel is it.
Before inspecting or servicing the engine compartment, there-
fore, remove the ignition switch key.
3. ACTIONS TO BE TAKEN WHEN BATTERIES ARE DE-
PLETED
(a) Actions to be taken when the auxiliary battery is depleted
HINT:
The following phenomena indicate that the auxiliary battery is
depleted:

No display appears on the instrument panel when you
turn the ignition switch to the ON position.

The hybrid system does not start.

The headlights are dark.

The sound from the horn is weak.
NOTICE:
Never use a quick charger.
(1) Move the shift lever to the P position, and engage
the parking brake.
(2) Remove the ignition key plate from the ignition
switch.
(3) Using a booster cable, connect the 12 V battery of
the rescue vehicle and auxiliary battery of the
stalled vehicle, as shown in the illustration.
(4) Start the engine of the rescue vehicle and run the
engine at a speed slightly higher than the idling
speed for 5 minutes to charge the auxiliary battery
of the stalled vehicle.
(5) Turn the ignition switch of the stalled vehicle to the
START position to start the hybrid system.
If the hybrid system fails to start and the master and HV battery
warning lights come on, the HV battery may have been dis-
charged.
(6) Disconnect the booster cable in the reverse way of
the connection procedure.
NOTICE:
If the auxiliary battery needs to be replaced, replace it only
with a 12 V battery specially designed for the use of the
PRIUS.