How to Fix P2121 Code On Cummins? (Completely Explained)

If you know driving, then the most basic thing about driving a car is pressing the accelerator pedal. It gives your car the required amount of torque. But what if the torque you want to move your car is not generating even after pressing the accelerator pedal at full pressure?

Well, it happens for the error code P2121. The P2121 code demonstrates an issue with the accelerator pedal position or APP sensor in your Dodge cummin truck.

Does it seem like a tough condition? No worries. This article is going to help you. Today we will give you an overview of the diagnostic trouble code P2121 and instruct you on how to solve this code accordingly.

P2121 Code On Cummins

What Does The P2121 Code Mean On Cummins?

Error code P2121 demonstrates an issue with the accelerator pedal position or APP sensor in your Dodge cummin. If you get a P2121 code, your car’s PCM has detected a problem in a specific APP sensor circuit.

The APP sensor determines the required torque and sends acceleration input to the PCM. There are two pedal position signal detectors in the sensor to ensure the PCM receives the correct input and gives the right amount of torque. Here,

  • P = OBD-II Diagnostic Powertrain (P) Trouble Code for Engine
  • 2 = Fuel and Air Metering (Injector Circuit Malfunctions Only)
  • 1 = Fuel Rail/System Pressure – Too High
  • 21= Specific fault code (Crankshaft Position Sensor A Low Circuit Input)

How serious is the P2121 code on Cummins?

The code P2121 can make your dodge Cummins undrivable. The seriousness of this error code depends on some factors.  Followings are the trouble you may face if you get a p2121 error code and do not fix it.

Start and Stall condition

It is a situation when your car engine does not get enough fuel to accelerate. In a case like p2121, the APP sensor sends the wrong signal to the PCM, and the PCM sends the wrong amount of fuel to the combustion chamber, which is sufficient enough to start the engine but not enough to accelerate.   

  • Poor Acceleration

This problem is the result of a stall condition. When your car engine lacks fuel, it faces difficulty accelerating.  

  • No- Start condition.

A damaged circuit in the APP sensor can stop sending signals and stop fuel flow from reaching the engine combustion. 

What Causes The P2121 Code On Cummins?

Many identified causes can lead to the p2121 error code of your acceleration pedal position sensor. Following are the common causes that might be why your car engine is facing this p2121 issue.

  • Faulty APP sensor because of damaged cables or damaged connections on the accelerator pedal sensor
  • Missing voltage and ground supply
  • APP Sensor harness is open or shorted
  • Faulty Powertrain Control Module (PCM)
  • Faulty electronic evaluation unit in the sensor
  • Sensor circuit poor electrical connection

How To Fix The P2121 Code On Cummins?

To fix this issue with diagnosis and repair, you should visit an auto workshop, or if you want to fix it by yourself as a DIY project, then you will need an OBD-II scanner/code reader, a digital Voltmeter, an Oscilloscope, and the service manual of the manufacturer.  

NB: It is to clarify that the p2121 code is applicable on vehicles that have an acceleration body of drive by wire. 

Now to fix the issue, follow the following steps outlined: 

Situation one:

Take inspection of all the wiring and connectors there.

If you find any wiring broken or disconnected, corroded or shorted, then those components should be fixed or replaced to ensure the wiring connections are okay.

If all the connections are okay, attach the scan tool reader with the diagnostic connector; in this step, any saved code should be recorded, and data should be frozen. It will help see if codes return; if it returns, clear the codes and test drive the vehicle.   

Situation two:

Remove the connector from the APP sensor to check the voltage signals. Use the DVOM and check the voltage level. It should be of the 5-volt reference signal, and a battery voltage should be available. 

Disconnect the connector at the PCM if there is no identified reference voltage; check the resistance voltage of any controller connectors that are connected to it. Now repair or replace the APP circuit if needed. 

Clear the code and make a test drive. 

Situation three: 

Replace the accelerator actuator motor if there is any detected voltage indication in the connector 

Clear the code from the device and make a test drive to see if everything is okay.

Other Symptoms Of Getting A P2121 Code On Cummins 

Your Cummins may get a p2121 error because of the causes mentioned above, but other symptoms may indicate a problem with the APP. 

  • Black Smoke at startup

Black smoke does not always mean your car has been damaged or your combustion chamber is faulty. If at the start of your car you see a black smokescreen, it can mean there is a problem in the amount of fuel getting to the combustion because of the APP sensor issue.

  • Misfire at idle

The ignition system performs the duty of igniting fuel in the engine, and if there is any problem in the ignition system, it may cause a misfire. On many occasions, it can result from an APP sensor issue. 

  • Forced idle 

When your car engine does not get enough fuel to generate enough torque, it gradually goes to idle even after pressing the accelerator pedal.

  • Forced shutdown 

Forced shut down is the next level situation of forced idle caused by APP sensor fault p2121. 

What Is The Cost To Fix The P2121 Cummins Code?

The cost of fixing the p2121 issue depends on the skill level of labor and the type of car you are using. In most cases, the average labor cost to fix this p2121 issue is one labor hour, and the monetary cost to fix the issue is around $80-150 dollars.

Can You Drive Your Cummins With Code P2121?

Yes, in some cases, you may start your car and drive. But it is recommended to visit the technician and fix the issue without any delay. P2121 issue is related to the acceleration of your car by generating torque.  The following problems may occur if you drive with this code:

  • Damaged the app sensor and not being able to move the car at all.
  • Driving the car with light symptoms and facing an accident on the highway.


Dodge Cummins with a p2121 issue should not be driven in the street. There is a chance that the vehicle will totally stop moving or functioning or can suddenly go idle in the middle of traffic or the high-speed expressway.

In many cases, this acceleration sensor-related issue imposes the threat of accident because of a mismatching amount of torque generation.

So it is recommended if you get any p2121 issues with Cummins or see any symptoms which are related to the p2121 issue, you should immediately fix the problem for the safety of both you and the vehicle.

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