Advanced Diagnostics

Advanced Diagnostics - DTC P2138: Accelerator Pedal Position (APP) Sensor A/B (Throttle Position (TP) Sensor D/E) Incorrect Voltage Correlation (Engine Type: K24Z7)

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, APP sensors A and B detect the accelerator pedal opening value. The accelerator pedal opening value is converted to a signal in APP sensors A and B and transmitted to the engine control module (ECM) to compute the target position. APP sensor A is the primary control, and APP sensor B is a back-up of APP sensor A in case it malfunctions. 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 detects a malfunction and stores a DTC.

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






Enable Conditions






Malfunction Threshold
One of these conditions is met for at least 300 milliseconds:
- The APP sensor B voltage [APP SENSOR B] exceeds the range from 0 V or less to 0.37 V or more when the APP sensor A voltage [APP SENSOR A] is 0.37 V.
- The APP sensor B voltage [APP SENSOR B] exceeds the range from 2.31 V or less to 2.69 V or more when the APP sensor A voltage [APP SENSOR A] is 5.0 V.

[ ]: HDS Parameter

Possible Cause

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

- APP sensor failure
- APP sensor A APS1 line short to APP sensor B APS2 line
- ECM internal circuit failure

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 ECM 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.