Throttle/Pedal Position Sensor/Switch ”A” Circuit Malfunction - Toyota T100 1996 Service Manual

DTC P0120
CIRCUIT DESCRIPTION
Throttle Position
Sensor
DTC No.
Condition (a) or (b) continues:
P0120 (a) VTA < 0.1 V, and closed throttle position switch is OFF
(b) VTA > 4.9 V
HINT:
If there is open circuit in IDL line, DTC P0120 does not indicate.
S
After confirming DTC P0120 use the OBD II scan tool or TOYOTA hand−held tester to confirm the
S
throttle valve opening percentage and closed throttle position switch condition.
Throttle valve fully closed
0 %
100 %
1996 TOYOTA T100 (RM449U)
DIAGNOSTICS
Throttle/Pedal Position Sensor/Switch "A"
Circuit Malfunction
ECM
5 V
VCC
B+
VTA
IDL
E2
FI6571
DTC Detecting Condition
Throttle valve opening position
expressed as percentage
Throttle valve fully open
− ENGINE (3RZ−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, the IDL contacts in the throttle position sensor
are on, so the voltage at terminal IDL of the ECM becomes
0 V. At this time, a voltage of approximately 0.3 − 0.8 V is applied
to terminal VTA of the ECM. When the throttle valve is opened,
the IDL contacts go off and thus the power source voltage of
approximately 12 V in the ECM is applied to terminal IDL of the
ECM. The voltage applied to terminal VTA of the ECM in-
creases in proportion to the opening angle of the throttle valve
and becomes approximately 3.2 − 4.9 V when the throttle valve
is fully opened. The ECM judges the vehicle driving conditions
from these signals input from terminals VTA and IDL, and uses
them as one of the conditions for deciding the air−fuel ratio
correction, power increase correction and fuel−cut control etc.
S Open or short in throttle position sensor circuit
S Throttle position sensor
S ECM
0 %
100 %
Trouble Area
Trouble Area
VCC line open
VTA line open or short
E2 line open
DI−39
DI0TH−03