2001 TOYOTA PRIUS display

IN±38± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
2001 PRIUS (RM778U)
5. PROBLEM SYMPTOMS TABLE
The suspected circuits or parts for each problem symptom are shown in the table below. Use this table to
troubleshoot the problem when a ºNormalº code is displayed in the diagnostic trouble code check but the
problem is still occurring. Numbers in the table indicate the inspection order in which the circuits or parts
should be checked.
HINT:
When the problem is not detected by the diagnostic system even though the problem symptom is present,
it is considered that the problem is occurring outside the detection range of the diagnostic system, or that
the problem is occurring in a system other than the diagnostic system.
Symptom
Suspect AreaSee page
Engine does not crank (Does not start)
No initial combustion (Does not start)
No complete combustion (Does not start)1. Starter and starter relay
1. ECM power source circuit
2. Fuel pump control circuit
3. Engine control module (ECM)
1. Starter signal circuit
2. Fuel pump control circuit1. Fuel pump control circuitDI±147
DI±151
IN±29
PROBLEM SYMPTOMS TABLE
1. Compression
2. Fuel pump control circuit 1. A/C signal circuit
2. Fuel pump control circuit 1. A/C signal circuit (Compressor circuit)
2. ECM power source circuit 1. Starter signal circuit
2. Fuel pump control circuit1. Starter signal circuit
2. Fuel pump control circuit
3. Compression
idling) High engine idle speed (Poor idling) Hot engine Cold engine (Difficult to start)Engine cranks normally (Difficult to start)
AC±88 DI±144
DI±151
EM±3 DI±151

Problem Symptom
Page
Indicates the page where the flow chart for each circuit
is located.

Circuit Inspection, Inspection Order
Indicates the circuit which needs to be checked for each problem
symptom. Check in the order indicated by the numbers.

Circuit or Part Name
Indicates the circuit or part which needs to be checked.
ST±2
ST±17
DI±144
DI±151
DI±144
DI±151

IN±48
± INTRODUCTIONTERMS
48 Author: Date:
2001 PRIUS (RM778U) H/B
Hatchback
H±FUSEHigh Current Fuse
HIHigh
HIDHigh Intensity Discharge (Head Lamp)
HSGHousing
HTHard Top
HVHybrid Vehicle
HWSHeated Windshield System
IACIdle Air Control
ICIntegrated circuit
IDIIndirect Diesel Injection
IFSIndependent Front Suspension
IGIgnition
IIAIntegrated Ignition Assembly
INIntake (Manifold, Valve)
INTIntermittent
I/PInstrument Panel
IRSIndependent Rear Suspension
J/BJunction Block
J/CJunction Connector
KDKick±Down
LANLocal Area Network
LBLiftback
LCDLiquid Crystal Display
LEDLight Emitting Diode
LHLeft±Hand
LHDLeft±Hand Drive
L/H/WLength, Height, Width
LLCLong±Life Coolant
LNGLiquified Natural Gas
LOLow
LPGLiquified Petroleum Gas
LSDLimited Slip Differential
LSP & PVLoad Sensing Proportioning And Bypass Valve
LSPVLoad Sensing Proportioning Valve
MAX.Maximum
MG1Motor Generator No. 1
MG2Motor Generator No. 2
MICMicrophone
MILMalfunction Indicator Lamp
MIN.Minimum
MPMultipurpose
MPXMultiplex Communication System
M/TManual Transmission
MTMount
MTGMounting

N09214
FI2547
± DIAGNOSTICSENGINE
DI±5
2001 PRIUS (RM778U)
(b) Check the DLC3.
The vehicle's ECM uses ISO 9141±2 for communication.
The terminal arrangement of DLC3 complies with SAE
J1962 and matches the ISO 9141±2 format.
Terminal No.Connection / Voltage or ResistanceCondition
7Bus  Line / Pulse generationDuring transmission
4Chassis Ground / e Body Ground 1 W or lessAlways
5Signal Ground / e Body Ground 1 W or lessAlways
16Battery Positive / e Body Ground 9 ± 14 VAlways
HINT:
If your display shows ºUNABLE TO CONNECT TO VEHICLEº
when you have connected the cable of the TOYOTA hand±held
tester or OBDII scan tool to DLC3, turned the ignition switch ON
and operated the scan tool, there is a problem on the vehicle
side or tool side.

If communication is normal when the tool is connected to
another vehicle, inspect DLC3 on the original vehicle.

If communication is still not possible when the tool is con-
nected to another vehicle, the problem is probably in the
tool itself, so consult the Service Department listed in the
tool's instruction manual.
2. INSPECT DIAGNOSIS (Normal Mode)
(a) Check the MIL
(1) The MIL comes on when the ignition switch is turned
ON and the engine is not running.
HINT:
If the MIL does not light up, troubleshoot the combination meter
(See page BE±42).
(2) When the engine started, the MIL should go off. If
the lamp remains on, the diagnosis system has de-
tected a malfunction or abnormality in the system.
(b) Check the DTC.
NOTICE:

If there is no DTC in the normal mode, check the 1st
trip DTC using Continuous Test Result function
(Mode 7 for SAE J1979) or the TOYOTA hand±held
tester or OBDII scan tool.

DI±12
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
7. ENGINE OPERATING CONDITION
NOTICE:
The values given below for ºNormal Conditionº are representative values, so a vehicle may still be
normal even if its value varies from those listed here. So do not decide whether a part is faulty or
not solely according to the ºNormal Conditionº here.
(a) CARB mandated signals.
TOYOTA hand±held tester displayMeasurement ItemNormal Condition*
FUEL SYS #1
Fuel System Bank 1
OPEN: Air±fuel ratio feedback stopped
CLOSED: Air±fuel ratio feedback operating
Idling after warming up: CLOSED
CALC LOAD
Calculator Load:
Current intake air volume as a proportion of max.
intake air volumeIdling: 5.4 ± 19.2 %
Racing without load (2,250rpm): 6.9 ± 16.2 %
COOLANT TEMP.Engine Coolant Temp. Sensor ValueAfter warming up: 80 ± 95°C (176 ± 203°F)
SHORT FT #1Short±term Fuel Trim Bank 10 ± 20%
LONG FT #1Long±term Fuel Trim Bank 10 ± 20%
ENGINE SPDEngine SpeedIdling: 1,000 rpm
VEHICLE SPDVehicle SpeedVehicle Stopped: 0 km/h (0 mph)
IGN ADVANCEIgnition Advance:
Ignition Timing of Cylinder No. 1Idling: BTDC 7 ± 15°
INTAKE AIRIntake Air Temp. Sensor ValueEquivalent to Ambient Temp.
MAF/AFMAir Flow Rate Through Mass Flow Meter
Idling: 1.11 ± 4.38 gm/sec.
Racing without load (2,250 rpm):
3.38 ± 7.88 gm/sec.
THROTTLE POS
Voltage Output of Throttle Position Sensor
Calculated as a percentage:
0 V "0%, 5 V "100%Throttle Fully Closed: 0 ± 5 %
Throttle Fully Open: 90 ± 100 %
O2S B1, S1Voltage Output of Heated Oxygen Sensor Bank
1, Sensor 1Idling: 0.1 ± 0.9 V
O2FT B1, S1Heated Oxygen Sensor Fuel Trim Bank 1, Sen-
sor 1 (Same as SHORT FT #1)0 ± 20 %
O2S B1, S2Voltage Output of Heated Oxygen Sensor Bank
1, Sensor 2Driving at 50 km/h (31 mph): 0.1 ± 0.9 V
*: If no conditions are specifically stated for ºldlingº, it means the shift lever is at P position, the A/C switch
is OFF and all accessory switches are OFF.
(b) TOYOTA Enhanced Signals.
TOYOTA hand±held tester displayMeasurement ItemNormal Condition*
MISFIRE RPMEngine RPM for first misfire rangeMisfire 0: 0 rpm
MISFIRE LOADEngine load for first misfire rangeMisfire 0: 0 g/r
INJECTORFuel injection time for cylinder No.1Idling: 1.0 ± 3.0 ms
CYL#1, CYL#2, CYL#3, CYL#4Abnormal revolution variation for each cylinder0 %
IGNITIONTotal number of ignition for every 1,000 revolu-
tions0 ± 2,000
FUEL PUMPFuel Pump SignalIdling: ON
EVAP (PURGE) VSVEVAP VSV SignalVSV operating: ON
VAPOR PRESS VSVVapor Pressure VSV SignalVSV operating: ON
TOTAL FT B1Total Fuel Trim Bank 1: Average value for fuel
trim system of bank 1Idling: 0.8 ± 1.2 V

DI6UT±02
DI±14
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DIAGNOSTIC TROUBLE CODE CHART
HINT:
Parameters listed in the chart may not be exactly the same as your reading due to the type of instru-
ment or other factors.
If a malfunction code is displayed during the DTC check in check mode, check the circuit for that code
listed in the table below. For details of each code, turn to the page referred to under the ''See page
'' for the respective ''DTC No.'' in the DTC chart.
When the ignition switch is ON and ºREADYº indicator light is OFF, the bulb check of the ºMILº is per-
formed (ºMILº is ON).
When ºMILº is ON, but the DTC of the engine is not memorized, it may be because of HV control system
abnormality, so check HV control system beforehand.
SAE CONTROLLED:
DTC No.Detection ItemTrouble AreaMIL*1Memory
P0100
(DI±23)Mass Air Flow Circuit Malfunc-
tionOpen or short in mass air flow meter circuit
Mass air flow meter
ECM

P0101
(DI±27)Mass Air Flow Circuit Range/
Performance ProblemMass air flow meter
P0110
(DI±28)Intake Air Temp. Circuit Malfunc-
tionOpen or short in intake air temp. sensor circuit
Intake air temp. sensor (built into mass air flow meter)
ECM

P0115
(DI±32)Engine Coolant Temp. Circuit
MalfunctionOpen or short in engine coolant temp. sensor circuit
Engine coolant temp. sensor
ECM

P0116
(DI±36)Engine Coolant Temp. Circuit
Range/Performance ProblemCooling system
Engine coolant temp. sensor
P0120
(DI±38)Throttle/Pedal Position Sensor/
Switch ºAº Circuit MalfunctionOpen or short in throttle position sensor circuit
Throttle position sensor
ECM

P0121
(DI±43)Throttle/Pedal Position Sensor/
Switch ºAº Circuit Range/Perfor-
mance ProblemThrottle position sensor
ECM
P0125
(DI±44)Insufficient Coolant Temp. for
Closed Loop Fuel Control
Open or short in heated oxygen sensor (bank 1 sensor 1)
circuit
Heated oxygen sensor (bank 1 sensor 1)
Air induction system
Fuel pressure
Injector
Gas leakage on exhaust system
ECM

P0128
(DI±49)Thermostat Malfunction
Thermostat
Cooling system
Water temperature
ECM

P0130
(DI±50)Heated Oxygen Sensor Circuit
Malfunction (Bank 1 Sensor 1)
(Except Calif.)
Open or short in heated oxygen sensor circuit
Heated oxygen sensor
Air induction system
EGR system
Fuel pressure
Injector
ECM


FI4741
(fig.1)
Acceptable
Resistance kW
± 20 0 20 40 60 80 100
(± 4) 32 68 104 140 176 212 30
20
10
5
3
2
1
0.5
0.3
0.2
0.1
Te m p .°C (F°)
DI±28
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DTC P0110 Intake Air Temp. Circuit Malfunction
CIRCUIT DESCRIPTION
The intake air temp. sensor is built into the mass air flow meter
and senses the intake air temperature.
A thermistor built in the sensor changes the resistance value
according to the intake air temperature, the lower the intake air
temperature, the greater the thermistor resistance value, and
the higher the intake air temperature, the lower the thermistor
resistance value (See fig.1).
The air intake temperature sensor is connected to the ECM
(See below). The 5V power source voltage in the ECM is ap-
plied to the intake air temp. sensor from the terminal THA via
a resistor R.
That is, the resistor R and the intake air temp. sensor are con-
nected in series. When the resistance value of the intake air
temp. sensor changes in accordance with changes in the intake
air temperature, the potential at terminal THA also changes.
Based on this signal, the ECM increases the fuel injection vol-
ume to improve driveability during cold engine operation.
If the ECM detects the DTC ºP0110º, it operates the fail safe
function in which the intake air temperature is assumed to be
20°C (68°F).
DTC No.DTC Detecting ConditionTrouble Area
P0110Open or short in intake air temp. sensor circuit

Open or short in intake air temp. sensor circuit

Intake air temp. sensor (built into mass air flow meter)

ECM
HINT:
After confirming DTC P0110, use the OBD II scan tool or TOYOTA hand±held tester to confirm the intake
air temperature from CURRENT DATA.
Temperature DisplayedMalfunction
±40°C (±40°F)Open circuit
140°C (284°F) or moreShort circuit
DI6UX±02

A00310
E1
Engine Coolant Temp.
Sensor
2
1ECM
W
BR14
E8
E8185V
THW
E2
E1 R DI±32
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DTC P0115 Engine Coolant Temp. Circuit Malfunction
CIRCUIT DESCRIPTION
A thermistor built into the engine coolant temp. sensor changes the resistance value according to the engine
coolant temp.
The structure of the sensor and connection to the ECM is the same as in the intake air temp. circuit malfunc-
tion shown on page DI±28.
If the ECM detects the DTC P0115, it operates fail safe function in which the engine coolant temperature
is assumed to be 80°C (176°F).
DTC No.Detection ItemTrouble Area
P0115Open or short in engine coolant temp. sensor circuit

Open or short in engine coolant temp. sensor circuit

Engine coolant temp. sensor

ECM
HINT:
After confirming DTC P0115, use the OBD II scan tool or TOYOTA hand±held tester to confirm the engine
coolant temp. from ºCURRENT DATAº.
Temp. DisplayedMalfunction
±40°C (±40°F)Open circuit
140°C (284°F) or moreShort circuit
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

If DTC P0110, P0115 and P0120 are output simultaneously, E2 (sensor ground) may be open.

Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame
records the engine conditions when the malfunction is detected, when troubleshooting it is useful for
determining whether the vehicle was running or stopped, the engine warmed up or not, the air±fuel
ratio lean or rich, etc. at the time of the malfunction.
DI6UY±02

A09300
Vehicle speed
40 km/h
(25 mph)
Idling(c)(d)
(e)
(a)
IG SW OFF
(b)
(e)
60 sec.
or more(d)
(d) Once
40 sec.
or moreTwice
40 sec.
or more11 times
40 sec.
or more
10 sec. 10 sec.(e)
10 sec.
± DIAGNOSTICSENGINE
DI±59
2001 PRIUS (RM778U)
DTC P0136 Oxygen Sensor Circuit Malfunction
(Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI±44.
DTC No.DTC Detecting ConditionTrouble Area
P0136
Voltage output of the heated oxygen sensor remains at 0.45 V
or more, or 0.55 V or less when the vehicle is driven at 40 km/h
(25 mph) or more after the engine is warmed up.
(2 trip detection logic).

Open or short in heated oxygen sensor circuit

Heated oxygen sensor
HINT:
Sensor 2 refers to the sensor farther away from the engine body.
WIRING DIAGRAM
Refer to DTC P0125 on page DI±44.
CONFIRMATION DRIVING PATTERN
(a) Connect the hand±held tester to the DLC3.
(b) Switch the hand±held tester from the Normal Mode to the Check (Test) Mode (See page DI±3).
(c) Start the engine and let the engine idle for 60 seconds or more.
(d) Drive the vehicle at 40 km/h (25 mph) or more for 40 seconds or more.
(e) Let the engine idle for 10 seconds or more.
(f) Preform steps (d) to (e) 11 times.
HINT:

During performing the steps (d) to (e) 11 times, drive the vehicle at over 65 km and make the fuel cut
happen for over 3 sec.

If a malfunction exists, the MIL will be indicated on the multi information display during step (f).
NOTICE:
If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a hand±held tester, turn the ignition switch OFF after performing steps (c) to (f),
then perform steps (c) to (f) again.
DI6V6±02