Toyota Celica 2005 Repair Manual page 279

DI−80
DTC P0110
CIRCUIT DESCRIPTION
(Fig.1)
30
20
10
5
3
2
1
0.5
0.3
0.2
0.1
− 20 0 20
(− 4) 32 68
Temp. _C (_F)
DTC No.
P0110 Open or short in intake air temperature sensor circuit
HINT:
After confirming DTC P0110, confirm the intake air temperature in the "DIAGNOSIS / ENHANCED OBD ll
/ DATA LIST / ALL" using the hand−held tester or OBD ll scan tool.
Temperature Displayed
−40°C (−40°F)
140°C (284°F) or more
MONITOR DESCRIPTION
The ECM monitors the sensor voltage and uses this value to calculate the intake air temperature. When the
sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the IAT
(Intake Air Temperature) sensor and sets a DTC.
Example:
The sensor voltage output equals to −40_C (−40_F), or more than 140_C (284_F).
2005 CELICA (RM1131U)
DIAGNOSTICS
Intake Air Temp. Circuit Malfunction
Acceptable
40 60 80 100
104 140 176 212
A21412
DTC Detecting Condition
− ENGINE (1ZZ−FE)
The intake air temperature (IAT) sensor, mounted on the mass
air flow (MAF) meter, monitors the intake air temperature. The
IAT sensor has a thermistor that varies its resistance depending
on the temperature of the intake air. When the air temperature
is low, the resistance in the thermistor increases. When the tem-
perature is high, the resistance drops. The variations in resis-
tance are reflected as voltage changes to the ECM terminal.
(See Fig. 1).
The intake air temperature sensor is connected to the ECM.
The 5 V power source voltage in the ECM is applied to the in-
take air temperature sensor from terminal THA via resistor R.
That is, the resistor R and the intake air temperature sensor are
connected in series. When the resistance value of the intake air
temperature sensor changes in accordance with 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 the driveability during cold engine operation.
S Open or short in intake air temp. sensor circuit
S Intake air temperature sensor (built into mass air flow meter)
S ECM
278
Trouble Area
Malfunction
Open circuit
Short circuit
DI37Z−17