How can I replace the accelerator pedal assembly?

What is the DTC - diagnostic trouble code ? No code tells you a part is bad . Diagnostic testing procedures are given for each code the vehicle can set . Your vehicle can set numerous code's for the electronic throttle control an not one of them tell's you out right to replace the throttle body or the APP sensors . Looking at factory service repair info for the code an doing diagnostic testing befor replacing any parts should be done.

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:
• Accelerator pedal position sensing
• Throttle positioning to meet driver and engine demands
• Throttle position sensing
• Internal diagnostics
• Cruise control functions
• Manage TAC electrical power consumption
The TAC system components include the following:
• The accelerator pedal position (APP) sensors
• The throttle body assembly
• The throttle actuator control module
• The powertrain control module (PCM)

Accelerator Pedal Position (APP) Sensor
The accelerator pedal assembly contains 2 individual APP sensors within the assembly. The accelerator pedal position (APP) sensors 1 and 2 potentiometer type sensors each with 3 circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
The APP sensors are used to determine the pedal angle. The control module provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module with signal voltage proportional to pedal movement. APP sensor 1 signal voltage is low at the rest position and increases as the accelerator pedal is applied. APP sensor 2 signal voltage is high at the rest position and decreases as the accelerator is applied.

Throttle Body Assembly
The throttle body assembly consists of the throttle body, the throttle position (TP) sensors, and the throttle actuator motor. The throttle body functions similar to a similar to a conventional throttle body with the following exceptions:
• An electric motor opens and closes the throttle valve.
• The throttle blade is spring loaded in both directions and the default position is slightly open.
• There are 2 individual TP sensors within the throttle body assembly.
The TP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
The TP sensors are used to determine the throttle plate angle. The control module provides each TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensors then provide the control module with signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens.

Your best bet , take it to a qualified repair shop.

DTC P2138: Accelerator Pedal Position (APP) Sensor 1-2 Correlation
Electronic throttle control problem .
The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:
• Accelerator pedal position sensing
• Throttle positioning to meet driver and engine demands
• Throttle position sensing
• Internal diagnostics
• Cruise control functions
• Manage TAC electrical power consumption
The TAC system includes the following components:
• The accelerator pedal position (APP) sensors
• The throttle body assembly
• The engine control module (ECM)

Accelerator Pedal Position (APP) Sensor
The accelerator pedal contains 2 individual accelerator pedal position (APP) sensors within the assembly. The APP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
The APP sensors are used to determine the pedal angle. The engine control module (ECM) provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors provide the ECM with signal voltage proportional to the pedal movement. The APP sensor 1 signal voltage at rest position is less than 1 volt and increases to more than 4 volts as the pedal is actuated. The APP sensor 2 signal voltage at rest position is less than 0.6 volt and increases to more than 2 volts as the pedal is actuated.
Search P2138 on youtube ,will show diagnostic steps .

No, most newer models have issues with the accelerator pedal and throttle body correlation switch assembly. Most need both switches replaced. One controls the intake and the other controls when you are depressing the pedal. Double check recalls, a lot of cars are getting recalled for some safety concerns involving acceleration. I hope that is what you meant by not accelerating. Does the engine rev up when you depress the gas pedal? Is the problem only when you have it in gear?

You need to replace the accelerator pedal assembly ! That's the whole gas pedal assembly , two bolts hold it fast to the fire wall . Search from over 10 Million Auto Parts P2138 APPS Accelerator Pedal Position Sensor Fix 3 5L Chevrolet Impala

ACEELERATOR PEDAL POSITION SENSOR IS USUALLY BUILT INTO ACCELERATOR PEDAL ASSEMBLY .........LOOK FOR WIRES COMING OUT OF ACCELERSTOR PEDAL ASSEMBLY ON THE INSIDE OF CAR NEAR OR UNDER ACC PEDAL ASSEMBLY

the pedal sensor is part of the gas peda assembly. The whole thing needs to be replaced if there is a problem with the sensor.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

This will probably make you do a "palm/forehead" but the pedal position sensor is part of the gas pedal assembly. In other words it is the part you push on with your foot to accelerate. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Hi, if you don't have a manual, you can get a free download here: http://www.dodge.com/en/owners/manuals/

The lightning bolt indicates a fault in the electronic throttle control. It is likely the rheostat/potentiometer in the accelerator position sensor is dirty or worn out. I have pasted info on the part below from autozone.com. If you replace the sensor, be sure to follow the calibration procedure at the end of the installation instructions. Please let me know if you have any questions and thanks for using FixYa.

Operation
The Accelerator Pedal Position Sensor (APPS) assembly is located under the vehicle battery tray. A cable connects the assembly to the accelerator pedal. A plastic cover with a movable door is used to cover the assembly.


NOTE The APPS is used only with the 5.7L V-8 engine.

The Accelerator Pedal Position Sensor (APPS) is a linear potentiometer. It provides the Powertrain Control Module (PCM) with a DC voltage signal proportional to the angle, or position of the accelerator pedal. The APPS signal is translated (along with other sensors) to place the throttle plate (within the throttle body) to a pre-determined position.
A mechanical cable is used between the accelerator pedal and the APPS assembly. Although a cable is used between the pedal and APPS, a mechanical cable is not used at the throttle body. Throttle plate position is electrically determined.
The Accelerator Pedal Position Sensor (APPS) assembly is located under the vehicle battery tray. A cable connects the assembly to the accelerator pedal. A plastic cover with a movable door is used to cover the assembly.


NOTE The APPS is used only with the 5.7L V-8 engine.

The Accelerator Pedal Position Sensor (APPS) is a linear potentiometer. It provides the Powertrain Control Module (PCM) with a DC voltage signal proportional to the angle, or position of the accelerator pedal. The APPS signal is translated (along with other sensors) to place the throttle plate (within the throttle body) to a pre-determined position.
A mechanical cable is used between the accelerator pedal and the APPS assembly. Although a cable is used between the pedal and APPS, a mechanical cable is not used at the throttle body. Throttle plate position is electrically determined.

Removal & Installation
The APPS is serviced (replaced) as one assembly including the sensor, plastic housing and cable. The APPS assembly is located under the vehicle battery tray. Access to APPS is gained from over top of left / front tire.

1. Disconnect negative battery cable at battery.
2. Disconnect APPS cable at accelerator pedal.
3. Remove wheel house liner at left / front wheel.
4. Gain access to APPS electrical connector by opening swing-down door.
5. Disconnect electrical connector.
6. Remove 3 mounting bolts.
7. Remove APPS assembly from battery tray.
8. If cable is to be separated at APPS, unsnap cable clip from ball socket. Release cable from plastic housing by pressing on small cable release tab.

To Install:

1. Install Accelerator Pedal Position Sensor (APPS) cable to accelerator pedal. Refer to Accelerator Pedal Removal / Installation.
2. Connect electrical connector to APPS.
3. If necessary, connect cable to APPS lever ball socket (snaps on).
4. Snap APPS cable cover closed.
5. Position APPS assembly to bottom of battery tray and install 3 bolts.
6. Install wheelhouse liner.
7. The 5.7L V-8 engine is equipped with a fully electronic accelerator pedal position sensor. If equipped with a 5.7L, also perform the following 3 steps:
   1. Connect negative battery cable to battery.
   2. Turn ignition switch ON, but do not crank engine.
   3. Leave ignition switch ON for a minimum of 10 seconds. This will allow PCM to learn electrical parameters.
      NOTE The DRB III Scan Tool may also be used to learn electrical parameters. Go to the Miscellaneous menu, and then select ETC Learn.
      
   
   
8. If the previous step is not performed, a Diagnostic Trouble Code (DTC) will be set.
9. If necessary, use a proper scan tool to erase any Diagnostic Trouble Codes (DTCs) from PCM.

it is the actual gas pedal. if you look you will see the module attached to the pedal. so the replacement should be the whole pedal assembly

APPS Accelerator Pedal Position Sensor is usually integrated to the pedal itself. If it has gone bad you have to replace the accelerator pedal assemble itself. 2 bolts/nuts and disconnect a wire harness.