What Is the P2121 Code on Dodge Cummins & How to Fix It?

“Throttle/Pedal Position Sensor/Switch D Circuit Range/Performance” is the diagnostic trouble code (DTC) P2121. This could also happen for a variety of reasons, and a mechanic would need to determine why this code was set in your case.

Continue reading to learn more about fixing P2121 Code on Dodge Cummins, covering possible causes, consequences, and other details.

An issue in a certain throttle position sensor circuit has been detected by the powertrain control module (PCM) or another similar control module. Modules that are related to each other include:

  1. Control module for transmission
  2. Control module for the body
  3. Control module for antilock brakes
  4. Control module for the instrument panel
  5. Control module for fuel injection
  6. Control module for turbojets
  7. Module to prevent stealing
  8. Module for cruise control
  9. Module for traction control
  10. Module for proximity alerts
  11. Module for climate control

What Does P2121 Code Mean on Dodge Cummins?

A fault code will be saved and the malfunction indicator lamp (MIL) will activate if the throttle actuator control motor circuit gives a reading to the PCM that is outside of normal specs.

Some models may require multiple drive cycles with a malfunction to activate the MIL, while others would do so right once.

Symptoms of Getting the P2121 Code on Cummins

Few the symptoms of getting the p2121 code are:

  • At first, there was a cloud of black smoke
  • sluggish acceleration
  • At idling, there is a misfire
  • Shutdown by force
  • Idle forcibly
  • Condition of start/stall
  • Condition of no-start

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The Causing Factors of the Error Code P2121

The several causing factors of the P2121 code are given below:

  • Control motor for the throttle actuator is defective.
  • A throttle position actuator that isn’t functioning perfectly.
  • A throttle position sensor or a pedal position sensor that isn’t working properly.
  • Wiring or connectors in the throttle actuator motor or the Controller         
  • Area Network are corroded, open, or shorted (CAN) harness for a bus
  • Ground strap for the control module is loose.
  • Ground wire that has been broken

How Serious Is the P2121 Code on Cummins?

The symptoms of a P2121 code can render the car undrivable. The ECM will detect that the accelerator pedal position sensor is not functioning properly if the voltage outputs of the VPA and VPA2 deviate from the standard.

The accelerator position sensor is the only common cause of the P2121 error code.

Read Also: What Is P2146 Code on Dodge Cummins? (How to Fix It)

How to Solve P2121 Error Code on Cummins?

For this diagnosis and repair, you’ll need an OBD-II scanner/code reader, a digital volt/ohmmeter (DVOM), an oscilloscope, and the manufacturer’s service manual.

It is to note that P2121 codes only apply to vehicles with a “drive-by-wire” throttle body that is operated electronically.

Depending on the driver input, the throttle actuator moves a gear that meshes with a bigger gear, allowing the throttle plate to open fast and unexpectedly or slowly. The steps to resolving this issue are outlined below:

  • Step-01: Start by visually inspecting all of the wiring and connectors.
  • Step-02: Any broken, disconnected, shorted, or corroded wiring, connectors, or components should be repaired or replaced as needed. After the repairs are finished, retest the system.
  • Step-03: Attach the scan tool reader to the diagnostic connector if all system wiring, connectors, and components are in excellent working order. Any saved codes should be recorded and the data should be frozen. To see if the codes return, clear them and test drive the vehicle. Remember that the MIL may need to be illuminated many times on some models.
  • Step-04: Disconnect the electrical connector from the throttle position sensor to perform a test. To check for voltage and ground signals, use the DVOM. There should be a 5-volt reference signal and a battery ground available. Exact wiring diagrams and connection views could be found in the manufacturer’s service manual.
  • Step-05: Disconnect the connector at the PCM if no reference voltage and/or ground can be discovered. Check the resistance and continuity of any controller connectors that are connected to it. As needed, repair/replace shorted/open circuits.
  • Step-06: Clear the codes and give the vehicle a test drive.
  • Step-07: Replace the throttle actuator motor if voltage/ground indications are detected at the connector, clear codes, and drive the vehicle.
  • Step-08: In many circumstances, the complete throttle body, including the actuator motor and throttle position sensor, will need to be replaced.
  • Step-09: Replacement of the pedal sensor may be required when the throttle body is replaced.
  • Step-10: If the voltage/ground signals are within the manufacturer’s specifications, monitor pedal sensor operation using an oscilloscope, seeking unusual voltage spikes or other glitches.

How Much Does It Cost to Solve The Error Code P2121?

A modest do-it-yourself modification of the pedal position sensor would cost far less than $114.99 in most circumstances.

It’s worth mentioning that most service firms will require at least one hour of labor to replace this sensor, which might add $20 to the bill depending on where you live.

Rebuilding or repairing a throttle can cost anywhere from $124 to several hundred dollars, depending on the application. Keep in mind that labor rates in these situations vary greatly, so shop about for the best hourly wage.

Read Also: What Is P2262 Code On Dodge Cummins? (How to Fix It)

Common Mistakes While Solving the P2121 Code

When several codes are registered, technicians frequently tackle the indications instead of the cause of the problem. When a controller communication code is present, codes related to lean exhaust, engine misfires, fuel injectors, and a variety of other codes can be easily misdiagnosed.

To improve your chances of a proper diagnosis and repair, remember to diagnose the codes in the sequence in which they were saved. The freeze-frame function on the scanner can aid in determining the sequence wherein codes were stored.

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Additional Comments to Consider Regarding the P2121 Code

A code like P2121 can be traced back to the CAN bus on automobiles built after 2008. The CAN bus is a collection of sensors, wiring harnesses, and connectors that allows data to be communicated between modules and handle nearly all of the vehicle’s electrical functions.

A technician with a specialist scanner, such as Autohex or Tech II, can diagnose and fix CAN-related difficulties, although it may be difficult for a non-professional mechanic to diagnose and repair.

Exploring each circuit, which could number in the hundreds, could take hours and hours.

A hard drive is required for proper CAN network operation to retain memory in the event of a complete system collapse; all it takes is one misplaced DVOM probe to cause a disaster.

A qualified technician using a specialized May scanner, on the other hand, can identify pin values and control module operation without causing a system meltdown.

Keep a lookout for any dangling engine or gearbox ground cables, straps, or wires that may have been left during recent repairs.

Many problems, such as a P2121, are beyond the scope of a non-professional mechanic’s expertise and should be left to a competent specialist. Factory-trained personnel, not non-professionals, are needed to service sophisticated CAN systems.


Vehicles with the code P2121 should not be driven since there’s a potential they’ll stop working or go into a weak state unexpectedly. If the car loses power suddenly while traveling in traffic, this could result in an accident.

I hope our conversation today gave you all of the information you needed. It was all over when it comes to the P2121 code on a Dodge Cummins.

Keep an eye on the code and try to fix it as quickly as possible. Consider all of my suggestions and, if required, seek professional help.

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