No one wants to see the Check Engine Light come on, especially when the motor performance seems to be suffering. With the P0122 code, you don’t have a lot of possible causes, so it can be easier to troubleshoot.
In this guide, I look at the meaning behind the P0122 trouble code. I also show you what causes it, the symptoms created by the fault, and I give you steps to fix it.
Code P0122 Definition
P0122 – Throttle Position Sensor/Switch A Circuit Low Input
What Does the P0122 Code Mean?
The P0122 trouble code signifies that the throttle position sensor or switch A circuit has a lower input than expected. The PCM is responsible for logging this code when the input doesn’t mean normal parameters.
The throttle position sensor is tasked with tracking the position of the throttle. The sensor sits on the throttle body in most configurations. The DTC could also indicate that something is wrong with the electronic throttle pedal, which is installed on most newer models.
The throttle position sensor sends off a signal telling the computer how to manage the fuel-to-air ratio. It’s also needed to run the emission system.
P0122 Trouble Code Symptoms
The symptoms exhibited by the vehicle will vary depending on what has gone wrong. While the Check Engine Light comes on every time the P0122 code is set, the other symptoms can vary.
Here are a few symptoms you might notice:
- Check Engine Light
- Difficulty starting engine
- Idle issues, either rough, low or high
- Hesitating engine
- Engine surging
- Trouble accelerating
Causes of the P0122 Code
There are multiple reasons that the P0122 code sets. Without a complete diagnosis, it’s difficult to know what’s wrong, which is why you want to follow the steps listed lower below.
Here are a few common causes:
- Throttle position sensor is mounted incorrectly/Not calibrated
- Electrical short/damaged wiring
- Damaged/bad throttle position sensor/switch
- PCM issues
How Serious is the P0122 Code?
Severe – When the P0122 code sets, the engine’s ECM goes into the failsafe or limp mode. During this time, you won’t have as much control over the vehicle as the speed will be automatically limited. If you are driving on a highway, this can lead to a serious issue.
Furthermore, whatever is causing the P0122 DTC can also lead to jerking, bucking and stalling. All of these are potential hazards, so it’s best to have them fixed.
What Repairs Can Fix the P0122 Code?
After a complete diagnosis, you will know what needs to be replaced or repaired. While these are the most common repairs, there could always be something else causing problems.
- Mount throttle position sensor correctly
- Calibrate throttle position sensor
- Repair electrical short/damaged wiring
- Replace throttle position sensor/switch
- Reprogram or replace PCM
Common P0122 Diagnosis Mistakes
The most common thing people do is to pass over the visual inspection first. It’s common to go ahead and replace the TPS without first ruling out that there’s an issue with its mounting or wiring.
We always recommend performing a complete inspection first. After that, you will have a better understanding of what’s wrong, so you don’t replace unnecessary parts.
How to Diagnose the P0122 Trouble Code
Even if you aren’t a professional technician, you can still troubleshoot your issues with the same steps. Here are the steps most mechanics take when dealing with the P0122 trouble code.
- Scan trouble codes. Reset the codes and go for a test drive to see what comes back.
- With freeze frame data, you can monitor the throttle position data. If it doesn’t match the specs set out in the service manual, there could be a problem with the sensor or its wiring.
- Double-check all of the connections and wiring. You should also verify that the TPS is mounted correctly. If not, adjust it to get proper measurements once again.
- Calibrate the throttle position sensor with a code scanner with the ability to do the job.
- If the wiring and mounting aren’t to blame, you may need to replace the sensor or switch.
- Beyond those steps, the problem could lie with the PCM. A reprogram or replacement might be necessary.
If you can’t figure out what’s causing the problem, it’s always best to consult with a professional mechanic. You don’t want to replace parts that are good.
Estimated Repair Cost
Once you have completed the diagnosis steps, you will have a better idea of what needs to be fixed. If you can’t repair the problem yourself, you will need to pay for the parts and labor. As an estimate, we show you some of the average costs associated with the most popular repairs.
- Mount throttle position sensor – $25-$75
- Repair electrical short/damaged wiring – $50-$500
- Replace throttle position sensor/switch – $100-$350
- Reprogram or replace PCM – $250-$2,500
Mechanics Tips about the P0122 Code
When the P0122 trouble code sets in your car computer, there are several others that you might notice. In fact, several codes indicate problems with the throttle position sensor in the A position. You could also see these codes:
- P0120: Throttle Position Sensor/Switch A Circuit Malfunction – this code shows the voltage rises or drops more than normal or otherwise stutters when compared to the “B” sensor
- P0121: Throttle Position Sensor/Switch A Circuit Range/Performance Problem – this code shows the throttle angle isn’t matching the expected value for the RPMs
- P0123: Throttle Position Sensor/Switch A Circuit High Input – this code suggests that the voltage is exceeding what’s considered normal
- P0124: Throttle Pedal Position Sensor/Switch (TPS) A Circuit Intermittent – this code shows that the sensor is sending erratic or intermittent signals during a certain period