2001 TOYOTA PRIUS O2 sensor

BE6653
A00370
A13622A13623
ON
Engine Coolant
Temp. Sensor
12
THWE2
ECM
5 V
E2THW
E1
BE6653
A00372A00373
ON
2
1ECM
Water Temp. Sensor
DI±34
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
3 Check for open in harness or ECM.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Connect between terminals THW and E2 of the ECM con-
nector.
HINT:
Engine coolant temp. sensor connector is disconnected. Be-
fore checking, do a visual and contact pressure check for the
ECM connector (See page IN±41).
(c) Turn the ignition switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA
hand±held tester.
OK:
Temperature value: 140°C (284°F) or more
OK Open in harness between terminals E2 or THW,
repair or replace harness.
NG
Confirm good connection at ECM. If OK,
check and replace ECM (See page IN±41).
4 Check for short in harness and ECM.
PREPARATION:
(a) Disconnect the engine coolant temp. sensor connector.
(b) Turn the ignition switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA
hand±held tester.
OK:
Temperature value: ± 40°C (± 40°F)
OK Replace engine coolant temp. sensor.
NG

A09085A09091
ON
Engine Coolant
Temp. Sensor
E8 Connector
ECM
5 V
E2THW
E1
± DIAGNOSTICSENGINE
DI±35
2001 PRIUS (RM778U)
5 Check for short in harness or ECM.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Disconnect the E8 connector of the ECM.
HINT:
Engine coolant temp. sensor connector is disconnected.
(c) Turn the ignition switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA
hand±held tester.
OK:
Temperature value: ±40°C (±40°F)
OK Repair or replace harness or connector.
NG
Check and replace ECM (See page IN±41).

DI±36
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DTC P0116 Engine Coolant Temp. Circuit Range/
Performance Problem
CIRCUIT DESCRIPTION
Refer to DTC P0115 on page DI±32.
DTC No.DTC Detecting ConditionTrouble Area
When the engine starts, the water temp. is ±7°C (20°F) or
less. And, 20 min. or more after the engine starts, the engine
temp. sensor value is 5°C (41°F) or less (2 trip detection logic)
When the engine starts, the water temp. is between ±7°C
(20°F) and 10°C (50°F). And, 5 min. or more after the engine
starts, the engine coolant temp. sensor value is 5°C (41°F) or
less. (2 trip detection logic)
P0116When the fluctuations in the engine coolant tempeerature are
within 3 °C (37 °F)before and afrer the follwing conditions are
met:
1. IDL OFF time  250 sec.
2. Vehicle speed change of 30 km/h (19 mph) or more occurs
10 times or more.
3. 35 °C (95 °F)
Engine coolant temperature when the
ignition switch is turned ON < 60 °C (140 °F)
4. Intake air temperature after starting the engine  ±6.7 °C
(20 °F)
Engine coolant temp. sensor

Cooling system
INSPECTION PROCEDURE
HINT:

If DTC P0115 and P0116 are output simultaneously, engine coolant temp. sensor circuit may be open.
Perform troubleshooting of DTC P0115 first.

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.
1 Are there any other codes (besides DTC P0116) being output?
YES Go to relevant DTC chart.
NO
DI6UZ±03

± DIAGNOSTICSENGINE
DI±37
2001 PRIUS (RM778U)
2 Check thermostat (See page CO±9).
NG Replace thermostat.
OK
Replace engine coolant temp. sensor.

A02396 A02395A02624
Throttle Position Sensor
Output Voltage (V)0 1.5
Accelerator Pedal Opening Angle (deg)70 125
VTA VTA2
5
VTA2 VTA E2 VCMovable Range
Usable RangeUsable Range *1*2
*1
*2
Movable Range
Usable
Range
*2
*1
Throttle valve
fully closed
Throttle valve
fully open *
2: *
1:
VTA2 circuit open or ground short
Accelerator pedal opening position expressed as percentage and voltage
Accelerator pedal releasedAccelerator pedal depressed
THROTTLE POS THROTTLE POS #2THROTTLE POS THROTTLE POS #2
0 %
0 %
100 % 8 ± 20 %0 V
2.0 ± 2.9 V
0 V
5 V0 %
0 %
100 %0 V
4.6 ± 5.1 V
0 V
5 VTrouble area
VC circuit open
VTA circuit open or ground short
E2 circuit open 64 ± 96 %
DI±38
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DTC P0120 Throttle/Pedal Position Sensor/Switch ºAº
Circuit Malfunction
CIRCUIT DESCRIPTION
Throttle position sensor is mounted on the throttle body and it have the 2 sensors to detect the throttle open-
ing angle and the malfunction of the throttle position sensor's own.
The voltage applied to the terminals VTA and VTA2 of the ECM changes between 0 V and 5 V in proportion
to the opening angle of the throttle valve.
The ECM judges the current opening angle of the throttle valve from these signals input from terminals VTA
and VTA2, and the ECM controls the throttle motor to make the throttle valve angle properly in response to
driving condition.
If this DTC is stored, the ECM shuts down the power for the throttle motor, and the throttle valve is fully closed
by the return spring.
DTC No.DTC Detecting ConditionTrouble Area
P0120
Condition (a), (b), (c), (d) or (e) continues for 2.0 seconds:
(a) VTA
0.2 V
(b) VTA2
0.625 V
(c) VTA  4.8 V
(d) When VTA  0.2 V and
2.0 V, and VTA2  4.97 V
(e) VTA ± VTA2
0.02 V

Open or short in throttle position sensor circuit

Throttle position sensor

ECM
Condition (a) continues for 0.4 seconds:
(a) VTA
0.2 V and VTA2
0.5 V
HINT:
After confirming DTC P0120, use the OBD II scan tool or TOYOTA hand±held tester to confirm the accelera-
tor pedal opening position percentage.
DI2DQ±07

A14051
T3
Throttle Position
SensorECM
2 3
PL E2
VC Y±R
BR232
21 18
VTA VC
VTA2 E2 E8
E8 E8
E8 (Shielded)
EB AJ9
J/C A J8
J/C
4 1 CC
BR
VTA2
VTA1 Y±R
FI7052
± DIAGNOSTICSENGINE
DI±39
2001 PRIUS (RM778U)
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

If DTCs P0110, P0115, P0120, P0450 and P1120 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 was warmed up or not, the air±fuel
ratio was lean or rich, etc. at the time of the malfunction.
LEXUS hand±held tester:
1 Connect LEXUS hand±held tester, and read throttle valve opening percentage.
PREPARATION:
(a) Connect the TOYOTA hand±held tester to the DLC3.
(b) Turn the ignition switch ON and push the TOYOTA hand±
held tester main switch ON.
CHECK:
Read the throttle valve opening percentage for VTA circuit and
read the voltage for VTA2 circuit.

A13624
ON
E2 VC
(+)
(±)
± DIAGNOSTICSENGINE
DI±41
2001 PRIUS (RM778U)
OK Check and replace ECM (See page IN±41).
NG
4 Check throttle position sensor (See page SF±24).
NG Replace throttle position sensor
(See page SF±29).
OK
Check for open and short in harness and connector in VC, VTA, VTA2 and E2 circuits between
ECM and throttle position sensor (See page IN±41).
OBD II scan tool (excluding TOYOTA hand±held tester):
1 Check voltage between terminals VC and E2 of ECM connector.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals VC and E2 of the ECM
connector.
OK:
Voltage: 4.5 ± 5.5 V
NG Check and replace ECM (See page IN±41).
OK

A13625
ON
VTAVTA2
E2
(+)
(±)
DI±42
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
2 Check voltage between terminals VTA and E2, and VTA2 and E2 of ECM connec-
tor.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals VTA and E2, and VTA2
and E2 of the ECM connector.
OK:
Alt dlVoltageAccelerator pedalVTA ± E2VTA2 ± E2
Released0.4 ± 1.0 V2.0 ± 2.9 V
Depressed3.2 ± 4.8 V4.6 ± 5.1 V
OK Check and replace ECM (See page IN±41).
NG
3 Check throttle position sensor (See page SF±24).
NG Replace throttle position sensor
(See page SF±29).
OK
Check for open and short in harness and connector in VC, VTA, VTA2 and E2 circuits between
ECM and throttle position sensor (See page IN±41).