P2121

DTC P2121 THROTTLE/PEDAL POSITION SENSOR/SWITCH "D" CIRCUIT RANGE/PERFORMANCE

HINT: This is repair procedure for the accelerator pedal position sensor.

CIRCUIT DESCRIPTION

DTC Detection Condition:

HINT:
This Electronic Throttle Control System (ETCS) does not use a throttle cable.

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. Voltage applied to VPA1 and VPA2 change between 0.2 V and 5 V depending on 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

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

The accelerator pedal position sensor is mounted on the accelerator pedal bracket and consists of two sensors VPA1 and VPA2. The VPA1 is used to detect accelerator pedal position, and the VPA2 is used to monitor the VPA1 and detect faults in the sensor itself. When the difference between voltage outputs of the VPA1 or VPA2 deviates from the standard range, the ECM concludes that there is a defect in the APP sensor. The ECM illuminates the MIL and sets a DTC.

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 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.

Wiring Diagram:

Step 1-3:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the hand-held tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.