P0122 Code: Meaning, Symptoms, Causes, Diagnostics, and Fixes

The P0122 code triggers when the “A” circuit on your vehicle’s throttle position sensor is giving too low of an input voltage. This sensor is used by your engine control module to track the position of the throttle. When it fails, your engine will activate failsafe mode. This makes any TPS code very important to clear as soon as possible.

For as serious as this code can be, the repairs are often fairly inexpensive and easy to make, even for a home mechanic. While you may need to replace the sensor, it may also simply be a problem with the wiring around it. Read on below to learn more about why this code triggers and how you can resolve the problem. 

The P0122 trouble code is rooted in the "A" circuit on the TPS
When the “A” circuit on the throttle position sensor is giving too low input voltage, the P0122 code is triggered

P0122 Code Definition

P0122 Code Definition (Generic): Throttle Position Sensor/Switch A Circuit Low Input

P0122 Dodge Code Definition: Throttle/Pedal Position Sensor/Switch “A” Circuit Low

P0122 Ford Code Definition: (TP) sensor circuit low input

P0122 Jeep Code Definition: Throttle/Pedal Position Sensor/Switch “A” Circuit Low

What Does P0122 Mean?

The throttle position sensor (TPS) monitors the movement of your throttle. When the throttle opens, it generates a voltage. The more open the throttle, the higher the voltage should be. This data is sent from the TPS to the engine control module (ECM), which monitors the overall engine performance.

The TPS has two circuits, labeled “A” and “B”. Each of these has a certain voltage range that it should report. When the “A” circuit output drops below the minimum voltage threshold, the P0122 trouble code is triggered.

Your exact TPS “A” circuit voltage range will vary depending on your vehicle’s manufacturer. Typically the lower limit should be around .2 volts, but you can find the specific voltage in your car’s manual. You’ll likely see this code appear alongside P0121 if the “B” circuit is operating correctly.

What Are The Symptoms Of The P0122 Code?

The symptoms of P0122 can vary. In most vehicles, it will activate your engine’s failsafe mode, cutting power to the actuator and reducing how far the throttle can open. This will limit your maximum speed and overall engine performance. 

Other common symptoms include:

  • Activation of the check engine light
  • Rough idling
  • Low or high idling
  • Stalls
  • Reduced acceleration or failure to accelerate
  • Engine surges

What Are The Causes Of P0122?

  • Incorrectly mounted TPS
  • Faulty or damaged wiring on the TPS
  • Short in the TPS ground
  • Faulty TPS
  • Damaged or faulty ECM

How Serious Is The P0122 Code?

The P0122 trouble code is serious. When your vehicle’s failsafe mode activates, you will have a lot of trouble accelerating and may experience frequent stalls. This makes your car unsafe to drive, as well as raising the potential risk for internal engine damage. You should avoid driving your vehicle until you’ve cleared this code.

How To Diagnose And Fix The P0122 Code

While P0122 is a generic powertrain code, the exact fixes may vary depending on your car’s make, model, and manufacturer. Check your manual for any recommended repair steps. You may also find technical service bulletins that have been released for your vehicle, suggesting specific repairs. Follow these first before proceeding with the generic diagnosis below. 

Tools You’ll Need:

The P0122 code can be diagnosed with an OBD2 code
Use an OBD2 scan tool to diagnose the P0122 code

Method:

  1. Scan your vehicle with an OBD2 scan tool to see if any other codes are present. You may see other trouble codes related to the TPS (P0120-P0124). Also read the freeze frame data to check what conditions were present when the code activated.
  2. Check the throttle position sensor to make sure it’s installed correctly. Very often, the P0122 code triggers if you don’t rotate the TPS when you’re installing it. The inside tab of the TPS must be in contact with the throttle body’s rotating pins in order to operate.
  3. Once you’ve correctly installed the TPS, verify all the connections are secure. Clear all codes using your OBD2 scanner and test drive your vehicle. Very often, this will fix the issue. If it doesn’t, continue with the diagnosis.
  4. Visually inspect all the wiring around the TPS. Replace any that are damaged or corroded.  Also check the connectors to make sure they’re not damaged.
  5. Compare the “A” and “B” circuit readings from your throttle position sensor. If they don’t match, check your vehicle manual for specific steps and tests to follow.
  6. Use a multimeter to check the voltage of the TPS. You can find the correct voltage in your vehicle’s manual. If it is too low, replace the TPS.
  7. Test the ground for the throttle position sensor using a digital multimeter. If the reading indicates an open or short, repair or replace it.

In some cases, the P0122 trouble code is an intermittent problem. You may find the code clears initially, only to recur a few days or weeks down the line. In these cases, drivers often don’t experience any symptoms aside from those associated with failsafe mode. This typically indicates a wiring issue. Re-check all the wiring around the TPS. If you can’t identify the specific problem, you may want to replace the entire harness. 

Common Mistakes To Avoid While Diagnosing The P0122 Code

Many inexperienced mechanics simply replace the throttle position sensor before they’ve verified this is the problem. Make sure you thoroughly inspect all the wires and connectors around the sensor before you replace any components. This will ensure you fix the entire problem. 

How to fix the P0122 code

Tips To Avoid P0122 In The Future

This code most commonly triggers after the throttle position sensor is replaced or adjusted, as a result of incorrect installation. Make sure you’re careful to correctly install any new components. This includes checking that all wires and connections are secure.  The wires of the throttle position sensor can be damaged by rubbing against the wiring harness. Double check the placement of the wires every time you install, replace, or adjust the sensor. Damaged wires are one of the main causes of TPS trouble codes, including P0122.

Read more: P0017 Code: Meaning, Symptoms, Causes, Diagnostics, and Fixes

Tim MillerFounderOBD Advisor

I’m Tim Miller from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about "Diagnostic Tools and Auto Repair". My fan page is facebook.com/autozikcom. I've been working as an automotive mechanic and blogger for over 10 years writing articles to share my experiences and expertise.

Web: https://www.obdadvisor.comEmail: [email protected]
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