The P0123 code - Definition, symptoms, causes (& how to fix)

The P0123 trouble code can be found when the Check Engine Light turns on, and your vehicle enters a failsafe mode. While it is a generic powertrain code, there’s a lot you can learn through diagnosis.

We will be focusing on the meaning of P0123 in this article. This article will also discuss the possible causes and symptoms, and offer solutions. 

Definition of the code P0123

P0123 – Throttle Position Sensor/Switch A Circuit High Input

What is the P0123 Code?

Three-terminal resistor A, which is attached to the shaft and throttle body, determines valve position. This sensor measures the angle of the throttle blade and transmits information back to either the throttle actuator module (powertrain control module) or the PCM (powertrain control modules). If the signal doesn’t respond properly, the P0123 code gets set. 

Electronic traction control will have two sensors for the accelerator pedal position. They measure angle of gas pedal. If there’s a problem with the APP sensors, this code could also be set. 

RELATED: Five Signs That Your Throttle Position Sensor Is Not Working (Replacement cost)

P0123 Trouble Code Symptoms

Check Engine Light is the most frequent symptom. The car will enter the failsafe mode in order to protect the engine.

These are some things that you may notice.

• Make sure your engine light is on
• The engine is in failsafe mode with reduced throttle
• More than the average idle
• Acceleration is not enough
• It is a rough idle

The P0123 Code: Causes

P0123 can have many causes. Most issues are related to either the throttle body or throttle position sensor.

Below are some possible reasons for the P0123 Code:

• Sensor for throttle position is not working properly
• Bad pedal position sensor
• Issues with sensor circuits, such as loose connections, wiring, or short circuits
• Bad throttle body or contamination
• Need to update PCM

Is the P0123 Code Really Serious?

High – The ECM switches to failsafe mode when P0123 is detected. This protects the transmission and engine from any damage. You will have difficulty getting your car to accelerate, or exceed a specified speed until the problem is fixed.

Failsafe mode only helps you to get home, and not leave you stranded. It’s very difficult to drive long distances because the car may exhibit a high idle, stalling, bucking and jerking along the way. Take the car to your mechanic immediately for repairs. 

How can you fix the code P0123?

P0123 can be repaired with a number of different methods. Before you spend money on parts, it is important to get a diagnosis. 

These are some of the most popular repairs.

Common mistakes in diagnosing P0123

It is a common mistake to make when diagnosing P0123 codes. You might, for example replace your throttle position sensor or pedal position sensor if the issue is a simple one of poor or defective wiring. 

When the throttle body is contaminated, you could replace or swap the throttle sensor. There’s also the chance that you replaced the pedal position sensor only to find out that something simple was messing with the angle, such as damaged floor mats. 

Diagnostic Tools

How do you diagnose the P0123 trouble code?

These are the steps a professional would follow to diagnose the P0123 code.

1. Use your engine code scanner with freeze frame data to see what’s happening with the car. To find out what happens, clean all fault codes. 
2. You can clean carbon from the throttle body using specialized cleaning agents. 
3. You should review any technical service bulletins that may be relevant to you. It is possible to save time by asking the manufacturer about your issue. 
4. Check the TPS connections and wiring for damage. Fix any problems with the wiring before you proceed.
5. Do a precise test of the TPS circuits A & B as described by the manufacturer in their service manual. Clear the codes and replace the TPS circuits A and B if necessary. 

Calculated Cost for Repair

Here’s an example of what you might spend to perform the necessary repairs.

• Replace TPS connector – $15-$75
• Repair wiring short – $15-$500
• Replace TPS sensor – $100-$300
• Clean/Replace throttle body – $10-$650

Here are some mechanics tips about the P0123 code

It’s not uncommon for the P0123 code to show up with other trouble codes. Manufacturer pinpoint tests will help you to identify the issue faster. 

TPS codes all aim to place the ECM in a failsafe mode. It doesn't matter the reason for this problem, drive symptoms will still be present until it is fixed.