2001 TOYOTA PRIUS Service Repair Manual

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
E8
E822
18ECM
5V
THA
E2
E1 R
R±B
BR 4
5 (Built into mass air flow meter)M1
Intake Air Temp. Sensor
± DIAGNOSTICSENGINE
DI±29
2001 PRIUS (RM778U)
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.
1 Connect OBD II scan tool or TOYOTA hand±held tester, and read value of intake
air temperature.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to DLC3.
(b) Turn the ignition switch ON and push the OBD II scan tool or TOYOTA hand±held tester main switch
ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA hand±held tester.
OK:
Same as actual air intake temperature.
HINT:

If there is open circuit, OBD II scan tool or TOYOTA hand±held tester indicates ± 40°C (± 40°F).

If there is short circuit, OBD II scan tool or TOYOTA hand-held tester indicates 140°C (284°F) or more.
NG ±40°C (±40°F) ....Go to step 2.
140°C (284°F) or more ....Go to step 4.
OK
Check for intermittent problems
(See page DI±3).

BE6653
A00347
A00348
ON
ECM
Intake Air
Temp. Sensor
4
5
Connecting
BE6653
A13620A00360A13621
ON
Intake Air
Temp. Sensor
54
THAE2
ECM
5 V
E2THA
E1 3
9
DI±30
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
2 Check for open in harness or ECM.
PREPARATION:
(a) Disconnect the intake temp. sensor connector.
(b) Connect sensor wire harness terminals together.
(c) Turn the ignition switch ON.
CHECK:
Read temp. value on the OBD II scan tool or TOYOTA
hand±held tester.
OK:
Temp. value: 140°C (284°F) or more
OK Confirm good connection at sensor. If OK,
replace intake air temp. sensor.
NG
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 THA and E2 of the ECM con-
nector.
HINT:
In take air temp. sensor connector is disconnected.
Before 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 THA,
repair or replace harness.
NG
Confirm good connection at ECM. If OK,
check and replace ECM (See page IN±41).