P2138 Code: Meaning, Symptoms, Causes & Fixes

DTC (Diagnostic Trouble Code) is a car method of onboard diagnostic (OBD) computer system that informs you that there is something wrong with your car. The onboard computer assigns a unique DTC code to each fault detected by the OBD computer system. P2138 code is one of the most famous diagnostic trouble codes. It triggers when your throttle position sensor or accelerator position sensor goes bad. This article explains the P2138 code symptoms and causes.

P2138 Code Definition

The P2138 code stands for “Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation.”

What does the P2138 Code Mean?

The P2138 code triggers when your powertrain control module (PCM) detects that the signals coming from the two throttle position sensors (or the two accelerator pedal position sensors) don’t correlate.

P2138 code

The throttle position sensor generates a voltage signal based on the throttle valve position. The further the throttle plate/valve is opened, the higher the output voltage of the throttle position sensor.

The accelerator position sensor tells your throttle body how far to open. It is located near the accelerator pedal.

The accelerator pedal position sensor tells the powertrain control module (PCM) how hard the accelerator pedal is pressed. PCM uses the data and compares it to pre-programmed parameters. The PCM then sends a signal to the throttle position sensor to open the throttle valve based on how hard the accelerator pedal is depressed. All of this takes place in a split second.

Next, the two throttle position sensors embedded in the throttle body convert the amount of throttle opening to a voltage signal sent to the PCM.

At last, the PCM detects the correlation of both of these voltage readings. When the voltages agree, the system operates as it should. However, when they deviate for two or more seconds, the PCM triggers the P2138 code to indicate a malfunction somewhere in the system.

Causes of P2138 Code

Symptoms of P2138 Code

  • Check engine light flashing
  • Higher fuel consumption than normal
  • Engine stalling
  • Hesitation under acceleration
  • Hard to start the car
  • Poor throttle response
  • Limp mode
  • A sudden reduction in the engine power
  • Rough or irregular idle
  • Poor acceleration

Read More: P2135 Code Symptoms and Causes

How To Diagnose the P2138 Code?

  • First of all, scan the P2138 using the OBD-II scanner.
  • Use the freeze frame data to check the main issue. After inspection, clear the code and make a test drive.
  • Inspect the throttle body wiring for damage or corrosion.
  • Inspect the connectors of the throttle body for damage.
  • Properly inspect the throttle body for damage. If the throttle body is clogged, properly clean it.
  • Inspect the throttle body sensor. If it is damaged, replace it.
  • Inspect the throttle position sensor wiring and connectors for damage.
  • Inspect the accelerator pedal position sensor wiring for disconnection, damage, or corrosion.
  • Properly inspect the working of the accelerator position sensor.
  • Inspect the throttle body motor for damage.
  • After all the above inspections and fixing, if your vehicle still shows the P2138 code, your PCM may have an issue. Replace or reprogram the PCM.

Common P2138 Code Diagnostic Mistakes

  • Replacing the throttle position sensor without inspecting the wiring and other parts.
  • Replacing the accelerator position sensor without inspecting the wiring and connectors.
  • Replacing the unnecessary components.
  • Installing the new parts without testing them.
  • Not cleaning the dirty throttle body.
  • Not clearing the PCM memory after fixing the error code.

What repairs can fix the P2138 Code?

  • Replacing the damaged or corroded throttle body sensor wiring
  • Replacing the accelerator position sensor
  • Repairing the faulty throttle body
  • Replacing the bad throttle position sensor
  • Replacing or repairing the damaged connectors of the throttle position sensor or accelerator position sensor
  • Cleaning the throttle body
  • Replacing the bad throttle body motor
  • Reprograming or replacing the PCM if needed

Repair Cost of P2138 Code

The fixing or repair cost of the P2138 code varies according to the vehicle model and the type of repair. Following are the major repair costs of P2138 which include the repair cost of the relevant parts and labor costs. 

PartsRepair Cost
Accelerator Position Sensor replacement$150 to $210
Throttle Position Sensor replacement$100 to $210
PCM replacement$240 to $3000
Throttle Body cleaning$190 to $320

FAQ Section

How serious is P2138 Code?

The P2138 code is considered to be serious. This is due to the fact that DTC P2138 is associated with the working correlation between signals from a vehicle’s throttle pedal and throttle plate.

This trouble code can cause the vehicle to lose its throttle response. If this happens at the wrong time, it could result in a wreck. Immediate repair is the only recommendation.

Can I drive with a P2138 Code?

It is not recommended to drive your car with the P2138 code as it can impair your ability to control your car’s acceleration. This can be very dangerous on the road and even lead to potential accidents and damage to your vehicle and others. This is why you should immediately take your car to a certified service station when confronted with the P2138 code.

How to reset a throttle pedal position sensor?

The easy method to reset the throttle position sensor is to disconnect the negative battery cable for about 5 minutes or remove the fuse from the powertrain control module (PCM).

Is disconnecting the battery reset the throttle position sensor?

Yes, you may reset the throttle position sensor by disconnecting the battery and reconnecting it after just a few seconds. This method will erase the code saved in the PCM and permit the sensor to relearn a free position.

How do I calibrate my accelerator pedal position sensor?

To realign the powertrain control module and accelerator pedal, turn the ignition switch in the ON position, then depress the accelerator pedal slowly and fully from idle to full throttle. Repeat this process 3 times.

Is the throttle position sensor the same as the accelerator pedal position sensor?

No, they are not the same. The throttle position sensor is located inside or on the throttle body of the engine. The accelerator pedal position sensor is located on the accelerator pedal inside the car.

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