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 in the engine compartment. APP sensors A and B are operated via the throttle linkage to determine the accelerator opening value when the driver presses the accelerator pedal. The accelerator pedal opening value is converted to a signal in APP sensors A and B and transmitted to the engine control module (ECM)/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 ECM/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 illuminating the MIL
When a malfunction is detected, the MIL comes on and the DTC and the freeze frame data are stored in the ECM/PCM memory.

Conditions for clearing the MIL
The MIL will be cleared if the malfunction does not recur during three consecutive trips in which the diagnostic runs. The MIL, the DTC, and the freeze frame data can be cleared by using the scan tool Clear command or by disconnecting the battery.