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P2138– What Does this Mean & How to Fix

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

The Diagnostic trouble code (DTC) P2138 stands for the “Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation.”

Meaning

This diagnostic trouble code (DTC) is a conventional Powertrain code. We view it as nonexclusive because it applies to all makes and models of vehicles (1996 - up to date), although clear/fix steps might be unique depending upon the model.

The DTC-P2138 code shows that the Engine Control Module (ECM)/Powertrain control module (PCM) has identified a malfunction inside the D or E circuits of the throttle /choke position sensor.

Or

Simply defining the P2138 problem related to the throttle’s ability to open and close properly.

Or

The powertrain control module (PCM) has noticed a disagreement in the voltage signal between a specific throttle position sensor (TPS) and a certain pedal position sensor (PPS).

Causes

You can do troubleshoot this code at home if you get understanding and knowledge about this issue. The usual suspects for a P2138 code are:

  • Defective Powertrain Control Module (PCM) or Engine Control Module (ECM) 
  • Circuit problems, such as spoiled wires or meager connections
  • A faulty throttle position sensor
  • The electronic throttle body is damaged
  • Damaged, wiring or sensor, of the accelerator pedal
  • The engine management computer has failed
  • There could be an issue in PCM, such as software needs to be updated

Symptoms

Symptoms of a P2138 code can be observed when a vehicle is running or standing idle. 

Here is what you’ll notice with a P2138:

  • Sudden loss of power at cruise speeds
  • The vehicle may not accelerate well (loss or lack of power)
  • The check engine light will illuminate, and the code will be set
  • Throttle (at any RPM) stuck.

Diagnosis

  • The diagnostic process of P2138 is usually a skilled work. A seasoned mechanic can detect this problem with his tools and accessories. But, one can do this check at home if he has the required skill, knowledge and suitable tools. You can use a vehicle information source, scanning device or decoder, which provides you data about which APP (accelerator pedal position) sensor is causing the problem. 
  • Lift the hood and locate the throttle body motor and throttle position sensor
  • You should check the connection and connecting wires
  • Either connector is connected, and the wires are in good conditions
  • Check either connectors are connected or not
  • Check the wires condition.   
  • Disconnect the connectors and inspect the conditions
  • Either the internal wires are good or damaged 
  • Also, examine dielectric grease on the terminals of connectors
  • Grease should be compatible with voltage. Terminal Grease should be compatible with voltage. If you are using 12 volts battery, terminal grease should be according to voltage requirements. 
  • To check the break in the sensor connector wiring use a Digital AVO meter. 
  • Use a digital AVO (ampere, voltage and ohm) meter to check the continuity of the sensor wire
  • Set the meter on ohm and touch the terminals with each other. You will hear a beep sound
  • Now use this technique to check the integrity of the cable
  • Use a multimeter/digital AVO to test the sensor and pedal connection terminals for defective or damaged wires
  • When the ignition is off, remove the cover of both connector and check the integrity of the connectors wire
  • If you hear a beep tone, then wires are good
  • If one wire reads pointedly higher than another, that shows that something is incorrect, and you’ll want to inspect that circuit
  1. To test faulty circuit voltage 
  • Now set the dial of the multimeter to DC voltages
  • Put the black terminal of the multimeter on the ground and another terminal to check the connector. Make sure that your battery is 12 volt and charge it
  • Put the car key and turn it on, but don’t start your car
  • If the voltage appears near 5 volts, then everything is good

This is a how you can check your vehicle for a P2138 error. Another method is to go to a mechanic shop and get it checked. 

Common mistakes

There is a low probability that you might be able to fix this specific issue all alone if you do not have a high-level output device and a computerized voltage scope with the right connections. You could think to fix the issue by replacing the “throttle position sensor”. But the concerns may still exist. It is recommended that an expert should inspect your vehicle.

How serious is this?

You should consider this error as pretty serious. If your car is not getting proper acceleration it could reduce the power of your car engine and stall the car. It is highly recommended to eliminate this issue correctly. 

What repairs can fix the code?

Following things/steps should be taken to fix your car. 

  • Replacement or repair of one or both TP sensors
  • Throttle position sensor repair or replacement along with associated wires with it 
  • Check all wires related to the accelerator pedal position and sensor circuit and replace or repair them if required. 

In short, you should replace or repair all the damaged components or parts.  

Related codes

In most cases, additional codes accompany P2138, and a loss of control of the throttle can be dangerous.

Other related error code includes

  • P2135 refers to the “Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation.”
  • P2136 refers to the “Throttle/Pedal Position Sensor/Switch A/C Voltage Correlation.” 
  • P2137 refers to the “Throttle/Pedal Position Sensor/Switch B/C Voltage Correlation.”
  • P2139 refers to the “Throttle/Pedal Position Sensor/Switch D/F Voltage Correlation.”
  • P2140 refers to the “Throttle/Pedal Position Sensor/Switch E/F Voltage Correlation.”

Conclusion

P2138 is a throttle/pedal position sensor/switch error. The pedal position sensor/switch is very fragile and should be handled with extreme care. If one doesn’t have any specific tool and training; it is recommended to contact with mechanic. Make sure to use owner manual for this specific issue.