P2121

3UZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P2121: Throttle / Pedal Position Sensor / Switch "D" Circuit Range / Performance

DTC P2121 - Throttle / Pedal Position Sensor / Switch "D" Circuit Range / Performance

DESCRIPTION

A vehicle that is equipped with an Electronic Throttle Control System (ETCS) does not have a throttle cable. The APP sensor is mounted on the accelerator pedal bracket. The APP 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. Voltage applied to VPA1 and VPA2 changes between 0.4 V and 4.8 V in proportion to the accelerator pedal angle.
The ECM monitors the accelerator pedal angle from VPA1 and VPA2 signal outputs, and controls the throttle actuator based on these signals.










MONITOR DESCRIPTION

When the difference between voltage outputs of VPA1 or VPA2 deviate from the standard range, the ECM concludes that there is a defect in the accelerator pedal position sensor. The ECM illuminates the MIL and sets the DTC. This monitor runs for 1 second (the first second of engine idle) after the engine is started.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





FAIL-SAFE

The accelerator pedal position sensor has 2 (main and sub) sensor circuits. If a malfunction occurs in either of the sensor circuits, the ECM detects the abnormal signal voltage difference between the 2 sensor circuits and changes to limp mode. In limp mode, the functioning circuit is used to calculate the accelerator pedal opening angle to allow the vehicle to continue driving. If both circuits malfunction, the ECM regards the opening angle of the accelerator pedal as being fully closed. In this case, the throttle valve remains closed as if the engine is idling.
If a "pass" condition is detected and the ignition switch is turned OFF, the fail-safe operation stops and the system returns to normal.

WIRING DIAGRAM





INSPECTION PROCEDURE
HINT:
- Read freeze frame data using the Techstream. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- This DTC is related to the accelerator pedal position sensor.

PROCEDURE

1. CHECK OTHER DTC OUTPUT
Result:






B -- GO TO RELEVANT DTC CHART
A -- Continue to next step.
2. REPLACE ACCELERATOR PEDAL
NEXT -- Continue to next step.
3. CHECK OUTPUT DTC (ACCELERATOR PEDAL POSITION SENSOR DTCS ARE OUTPUT AGAIN)
(a) Clear the DTCs DTC Check / Clear.
(b) Start the engine and allow the engine to idle for 15 seconds or more.
(c) Read DTCs.
Result:






B -- CHECK FOR INTERMITTENT PROBLEMS
A -- REPLACE ECM