Advanced Diagnostics

Advanced Diagnostics

DTC P2138: Accelerator Pedal Position (APP) Sensor A/B (Throttle Position (TP) Sensor D/E) Incorrect Voltage Correlation









General Description
Accelerator pedal position (APP) sensor A and accelerator pedal position (APP) sensor B are potentiometers. They are installed on the accelerator pedal. When the accelerator pedal is pressed, the APP sensors A and B detect the accelerator opening value. The accelerator pedal opening value is converted to a signal in APP sensors A and B and transmitted to the powertrain control module (PCM) to compute the target position. The target position signal is then transmitted to the throttle actuator control module. APP sensor A is for the primary control, and APP sensor B is a back-up. Both sensors compare their output voltage to each other for malfunction detection. When the voltage difference of APP sensor B is out of a fixed range for a set time, the PCM detects a malfunction, and a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
One of these conditions must be met for at least 300 milliseconds:
- APP sensor B voltage exceeds the range from 0 V or less to 0.37 V or more when the APP sensor A voltage is 0.37 V.
- APP sensor B voltage exceeds the range from 2.31 V or less to 2.69 V or more when the APP sensor A voltage is 5 V.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected, the MIL comes on and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM memory.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.