Toyota Celica 2005 Repair Manual page 295

DI−96
DTC P0120
CIRCUIT DESCRIPTION
Throttle Position
Sensor
DTC No.
Condition (a) or (b) continues for more than 5 sec.:
P0120 (a) VTA < 0.1 V
(b) VTA > 4.9 V
HINT:
After confirming DTC P0120, confirm the throttle valve opening percentage and closed throttle position
switch condition using the hand−held tester or the OBD ll scan tool.
Throttle valve closed
0 %
Approx. 100 %
MONITOR DESCRIPTION
The throttle position sensor varies its resistance with the angle of the throttle valve. The ECM applies a regu-
lated reference voltage to the throttle position sensor positive terminal and calculates the angle of the throttle
valve based on the current voltage at the throttle position sensor "signal" terminal.
When the throttle valve is near the fully closed position, the output voltage of the throttle position sensor is
low. When it is near the fully open position, the output voltage is high.
If the ECM detects that the output voltage of the throttle position sensor is out of the normal range, the ECM
interprets this as a malfunction in the throttle position sensor and sets a DTC.
2005 CELICA (RM1131U)
DIAGNOSTICS
Throttle Position Sensor/Switch "A"
Circuit Malfunction
ECM
VC
VTA
E2
P24296
DTC Detecting Condition
Throttle valve opening position
expressed as percentage
Throttle valve fully open
− ENGINE (1ZZ−FE)
The throttle position sensor is mounted in the throttle body and
detects the throttle valve opening angle. When the throttle valve
is fully closed, a voltage of approximately 0.3 to 0.8 V is applied
to terminal VTA of the ECM. The voltage applied to terminal VTA
of the ECM increases in proportion to the opening angle of the
throttle valve and becomes approximately 3.2 to 4.9 V when
the throttle valve is fully opened. The ECM judges the vehicle
driving conditions from this signal input from terminal VTA.
Based on the conditions, the air−fuel ratio, power increase, and
fuel−cut control, etc. are decided.
S Open or short in throttle position sensor circuit
S Throttle position sensor
S ECM
0 %
Approx. 100 %
294
Trouble Area
Trouble Area
VC circuit open
VTA circuit open or shorted
E2 circuit open
DIC6L−02