Toyota Celica 2005 Repair Manual page 601

DI−402
DTC P0121
HINT:
This is the procedure of "throttle position sensor".
CIRCUIT DESCRIPTION
Refer to DTC P0120 on page DI−391.
DTC No.
Condition (a) continues for 10 sec. with idling, but for 2 sec.
P0121 without idling :
(a) Difference between VTA and VTA2 is out of threshold
MONITOR DESCRIPTION
The ECM uses the throttle position sensor to monitor the throttle valve opening angle.
This sensor includes two signals, VTA1 and VTA2. VTA1 is used to detect the throttle opening angle and
VTA2 is used to detect malfunctions in VTA1. There are several checks that the ECM performs to confirm
proper operation of the throttle position sensor and VTA1.
There is a specific voltage difference between VTA1 and VTA2 for each throttle opening angle.
If the voltage output difference between the VTA1 and VTA2 deviates from the normal operating range, the
ECM interprets this as a malfunction of the throttle position sensor. The ECM will turn on the MIL and a DTC
is set.
FAIL SAFE
If the ETCS (Electronic Throttle Control System) has a malfunction, the ECM cuts off current to the throttle
control motor. The throttle control valve returns to a predetermined opening angle (approximately 16°) by
the force of the return spring. The ECM then adjusts the engine output by controlling the fuel infection (inter-
mittent fuel−cut) and ignition timing in accordance with the accelerator pedal opening angle to enable the
vehicle to continue at a minimum speed.
If the accelerator pedal is depressed firmly and slowly, the vehicle can be driven slowly.
If a "pass" condition is detected and then the ignition switch is turned OFF, the fail−safe operation will stop
and the system will return to normal condition.
MONITOR STRATEGY
Related DTCs
Required sensors/components
Frequency of operation
Duration
MIL operation
Sequence of operation
2005 CELICA (RM1131U)
DIAGNOSTICS
Throttle/Pedal Position Sensor/Switch "A"
Circuit Range/Performance Problem
DTC Detecting Condition
Main sensors/components
Related sensors/components
Continuous
2 sec.
Immediate
None
− ENGINE (2ZZ−GE)
Throttle body Assy (Throttle position sensor)
P0121
600
Trouble Area
Throttle position sensor rationality
Throttle position sensor
Vehicle speed sensor
DI383−16