DTC P2138
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, 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 powertrain control module (PCM) 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 or when the condition is met the PCM counts up, and if it counts up to a certain value, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type, OBD Status
| Execution | Continuous |
| Sequence | None |
| Duration | 300 milliseconds or more |
| DTC Type | One drive cycle, MIL on |
Enable Conditions
| Condition | |
|---|---|
| Vehicle | ON mode |
Malfunction Threshold
The APP sensor B voltage [APP Sensor B Voltage] is in the malfunction area based on the APP sensor A voltage [APP Sensor A Voltage] as shown in the figure below for at least 300 milliseconds or the PCM counts up to 570 or more.*
*: Counts down if it is in normal range [ ]: 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 AP1 line short to APP sensor B AP2 line
- PCM 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 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 12 volt battery.