Toyota Celica 2005 Repair Manual page 806

DTC P2121
HINT:
This is repair procedure for the "accelerator pedal position sensor".
CIRCUIT DESCRIPTION
Refer to DTC P2120 on page DI−597.
DTC No.
Condition (a) continues for 0.5 seconds:
P2121
(a) Difference between VPA and VPA2 is out of threshold
MONITOR DESCRIPTION
The accelerator pedal position sensor is mounted on the accelerator pedal bracket. The accelerator pedal
position sensor has 2 sensor elements/signal outputs: VPA1 and VPA2. VPA1 is used to detect the actual
accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA1. When
the difference between the voltage outputs of VPA1 and VPA2 deviates from the standard, the ECM con-
cludes the accelerator pedal position sensor has a malfunction. The ECM turns on the MIL and a DTC is
set.
FAIL SAFE
The accelerator pedal position sensor has two (main and sub) sensor circuits. If a malfunction occurs in ei-
ther of the sensor circuits, the ECM detects the abnormal signal voltage difference between the two sensor
circuits and switches to limp mode. In limp mode, the remaining circuit is used to calculate the accelerator
pedal opening to allow the vehicle to continue driving.
If both circuits malfunction, the ECM regards the opening angle of the accelerator pedal to be fully closed.
In this case, the throttle valve will remain closed as if the engine is idling.
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 "D"
Circuit Range/Performance
DTC Detecting Condition
Accelerator position sensor
Continuous
0.5 sec.
Immediate
None
− ENGINE (2ZZ−GE)
S Accelerator pedal position sensor circuit
S Accelerator pedal position sensor
S ECM
P2121
805
Trouble Area
Accelerator position sensor (rationality)
DI−607
DIC7T−02