What Does P0121 Code Mean on Chevy? Cause & Fix

The P0121 code means that it has problem with the throttle pedal position sensor. Engine Control Module (ECM) has learned that the throttle position “A” circuit’s voltage has either gone up or below the sensor’s safe range.

After receiving the code, you might be thinking how you can solve this issue. In this article you will know all about P0121 code on your Chevy and how to fix it.

What Does the P0121 Code Implicate on Chevy?

P0121 is an OBDII code that is associated with the throttle pedal positioning of a car. It is a quite serious problem because it can leave your car in an absolute halt.

Because it is a general powertrain code that means all the cars of other manufacturers also use this code for same type of problem.

P0121 can trigger in your Chevy if there is a problem with the throttle position sensor ‘A’ circuit. If the output voltage of the circuit goes above or below the safe range of the circuit, this code will be activated.

When this situation arises, ECM enters failsafe mode. The TPS is intended to transmit the input from pedal to the engine.

This allows the automobile to determine how much air to allow into the engine, for managing the vehicle’s acceleration.

If the sensor fails, it may not open at all. This will either cause the engine to die or cause the amount of speed to differ from the inputs

If there is any voltage signal that does not correspondent with the right RPM level then it is identified as a fault in the TPS circuit which causes P0121 code.

You will know more about this code and all the related information regarding this later on the article. Now, you should know what each letter and number means in P0121 –

• P- Powertrain, including engine, transmission and all the associate accessories.
• 0- A standardized SAE code, also known as generic code.
• 1- Fuel and air metering.
• 21- Throttle/Pedal Position Sensor.

Is the Code P0121 on Chevy a Serious Matter?

In most of the cases, the occurrence of code P0121 is met by an automatic system response. If the code occurs, vehicles management software restricts the flow of power to the engine.

Some cars may come to a hault, some cars may face severe problem in drivability.  Some cars may go into a limp mode of sorts.

If the issue came to throttle assembly then it can be quite serious. The flow of fuel or power to the engine stops because of problem in the throttle position sensor.

It can cause the car not to start.  It will also make the acceleration of the car quite impossible. So if not mitigated it can cause a serious problem.

The Causes of Code P0121 on a Chevy

There can be many reasons to cause code P0121 in you Chevy.  A 5V reference signal is given to the TPS and ground by the Powertrain Control Module or ECM.

When a car is idle its standard voltage is 5V and when in throttle 4.5V, or when the circuit receives more or less signal then the normal it causes P0121.

Here are some common causes:

• Faulty wiring connection.
• Sensor sends signals below or above the standard range.
• Corroded or faulty connector.
• Faulty sensor.
• Loose connection of TPS.
• Opening or short in the wiring.
• Faulty MAP sensor.

Other Symptoms of Getting P0121 Code on Chevy

When P0121 occurs there are some other symptoms that help to understand that this code can occur. Sometimes you may not notice the changes but sometimes there are big indications such as –

• Check engine light on.
• Reduced acceleration of the engine.
• Reduced speed of the car.
• No responds from throttle.
• Black smoke from tailpipe.
• Engine refusing to start.

How Can You Fix the P0121 Code on The Chevy?

At first, you have located the exact problem in your car that caused P0121 code. If you are not experienced or not confident enough you should contact with a professional.

Now, you should run a diagnosis to find the exact problem. As P0121 can occur by a faulty throttle position sensor, a faulty or damaged throttle body or damages in the wires or connectors, first check these for fixation.

1. Checking the Coolant Temperature Circuit

You can take help from the FIXD sensor which gives you live data of the throttle position sensor and also the throttle body temperature. Using the app you can read and analyze those data to properly diagnose the code P0121.

2. Cleaning the Throttle Body

Sometimes dirt in the throttles can cause dysfunction in the throttle position.  So you should clean the throttle body properly. If you don’t know how to do it you should contact a professional to do it properly for you.

3. Checking Connectors

You have to check all the connectors related to throttle body.  Sometimes the connectors can be corroded because of water or external factors.

Sometimes there are loose connections in the circuit. So you should tighten up all the connectors.

4. Test the Voltage

Normally if the difference between the voltages is above or below the standard the P0121 code occurs. So you should check the voltage of your car in different modes. If there is any inconvenience in the voltage difference.

5. Engine Control Module (ECM)

Engine Control Module or the ECM plays an important role in a car. So if there is any fault in the ECM, you should get it checked and fixed.

6. Electrical Connection

Faulty electrical connection can trigger P0121 code in a car. If there is any faulty electrical connection you should fix them or take the help of an expert to fix it for you.

7. Throttle Body Assembly Harness

You should check your throttle body assembly harness to be sure if it is open or shorted.

8. Sensors

There are many sensors connected to a car, they all work simultaneously.  Check all the sensors if they are working perfectly.

The Fixing Cost of the Chevy P0121 Code

Numerous things might cause this code, so to find the best path to a proper repair, some diagnostic work is required. One work hour is required to diagnose the P0121 error code.

This normally costs between $75 and $150, depending on the labor rate at the shop.

You might need one or more of the following fixes to resolve the P0121 error code. The estimated cost of repair includes the price of the necessary parts for each potential repair and prices are given below –

• Throttle Position Sensor (TPS) – $170 – $230
• Throttle Body Cleaning – $220 – $290
• Throttle Body – $580 – $690
• Wiring Repair or Replacement – $100 – $100

Is It Safe to Drive Your Chevy with the Code P0121?

When the P0121 error code appears, there is a problem with the throttle position sensor “A” circuit. It is best to cease driving as soon as your automobile has this problem.

P0121 is a critical check engine code that will lead your car to enter failsafe mode. As a result, you may have a variety of drivability difficulties such as restricted throttle response, harsh idling, banging, jerking, and stalling, and so on.

When the code appears, it is advisable to immediately stop driving. To prevent becoming stuck, the problem must be resolved as soon as possible.

Frequently Asked Questions (FAQs)

In this section, I will answer some frequently asked questions about the code P1249. Hopefully, you’ll find the solution you’re looking for in this area.

Conclusion

In this article, I have tried to give you enough information if you get the code p0121 on your car. Simply follow the steps outlined here to remove this code. Because a problem with the throttle component might cause your automobile to not start at all, it must be addressed as soon as possible.

If you are still unable to resolve the code on your own, please seek the assistance of a professional mechanic. Resolving the code requires a lengthy diagnostic, and assistance from an expert would be most beneficial in resolving this issue.