Toyota Celica 2005, Repair Manual

Page: 295 / 2497

P24296
Throttle Position
Sensor
VC
VTA
E2
ECM
DI − 96
− DIAGNOSTICS ENGINE (1ZZ − FE)
2005 CELICA (RM1131U)
DTC P0120 Throttle Position Sensor/Switch ”A”
Circuit Malfunction
CIRCUIT DESCRIPTION
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.
DTC No. DTC Detecting Condition Trouble Area
P0120
Condition (a) or (b) continues for more than 5 sec.:
(a) VTA < 0.1 V
(b) VTA > 4.9 V
S Open or short in throttle position sensor circuit
S Throttle position sensor
S ECM
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 opening position
expressed as percentage
Trouble Area
Throttle valve closed Throttle valve fully open
0 % 0 %
VC circuit open
VTA circuit open or shorted
Approx. 100 % Approx. 100 % E2 circuit open
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.
DIC6L − 02
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