P0123 – Meaning, Symptoms, Causes (& Hot To Fix it)

Throttle Position Sensor E1609870200166

What Does the P0123 Code Mean?

The P0123 code indicates a problem with the throttle/pedal position sensor. When the engine control module (ECM) detects that the throttle position sensor’s output voltage rating is exceeding the manufacturer specification, it generates the P0123 trouble code.
The throttle position sensor is just another name for a potentiometer and it is located on the throttle body while the pedal position sensor is associated with the accelerator pedal system. The throttle position sensor detects the movement of the accelerator pedal and based on the signal, the PCM determines how much power the engine requires. The P0123 code is triggered when the TPS switch voltage value is not within the specified range.

Definition: P0123 – Throttle Position Sensor/Switch A Circuit High Input

P0123 Symptoms

Here are some of the common symptoms associated with the P0123 trouble code.
• Hard Starting
• Rough engine performance
• Engine hesitation while accelerating
Check engine light illuminates
• Engine idling

Possible P0123 Causes

Here are some of the reasons why the P0123 trouble code generates.
• Throttle position sensor not positioned correctly
• Throttle position sensor short circuit
Defective throttle position sensor
• A defective pedal position sensor
• Contaminated throttle body
• Poor or damaged wiring

Possible P0123 Solutions

• Replace the throttle position sensor
• Clean or service the throttle position sensor
• Replace the pedal position sensor
• Service the throttle body
• Repair broken wire connections

How to Diagnose the P0123 Code?

Connect a Car Battery Charger

Before diagnosing the P0123 code, make sure to connect the car battery charger. When diagnosing the P0123 trouble code, your car’s engine will be switched on and this can cause the battery charge to deplete quickly. To avoid this situation, it is recommended that you attach a car battery charger before diagnosing the problem. If you do not have one at home, you can check out this one at Amazon: NOCO Genius G3500 6V/12V 3.5A UltraSafe Smart Battery ChargerIr?T=Askamastermec 20&Amp;L=Am2&Amp;O=1&Amp;A=B004Lwveks

Use the OBD2 Scanner

An OBD2 scanner is an exceptional tool to scan and monitor the trouble codes. The onboard diagnostic system is included in every car produced after 1996 and this standardized system is used for self-diagnostic and reporting. The OBD2 scanner has the ability to read and clear the codes as well as provide live data and record information.
Alternatively, you can use a digital multimeter which is cheaper, however, it lacks the functionality which is found in the OBD2 scanner.

Check for TPS wiring harness

Before replacing the sensor or carrying out other procedure, it is a good idea to check the wiring harness that leads to the throttle position sensor (TPS). Inspect the wiring and notice for any signs of damage or corrosion.

Inspect Throttle body assembly

Visually inspect the throttle body and see if it is dirty or contaminated. If it is, in fact, dirty, use a throttle body cleaner which can be found easily at any auto store or even eBay and Amazon. After cleaning the throttle, reset the code and see if the problem comes back again.

Test the Ground

Using a multimeter, test the ground voltage. Connect the red multimeter lead to the positive terminal of the battery and the black lead to the ground. If you notice that the reading is close to the battery voltage, then the ground is good. However, if not, there might be a problem with the power supply.

Testing the Sensor

On visual inspection, if you don’t find anything wrong with the throttle position sensor, it is time to test the voltage at the sensor. Set the digital multimeter to volt setting and study the vehicle wiring diagram to know which wire leads to where. Insert the black pin into the signal wire pin of the connector and the other pin to the ground. Open the throttle valve slowly and notice the reading. The voltage should increase as the throttle valve opens and with a wide open throttle, the ideal reading is 4.5 volts. At the idle position, the reading should be 0.45 volts.

Cleaning the Throttle Position Sensor and connector

Before you think of replacing the throttle/pedal position sensor, it is a good idea to first have the sensor cleaned and serviced as a dirty sensor transmits incorrect data to the PCM. To perform the servicing, you should have the following tools ready:

• Cleaning solution
• Clean cloth
• Screwdriver
• Gloves

Step 1: Let the engine run for a while

Start the car and let the engine idle for a few minutes. This will heat the internal components of the engine and some of the dirt will loosen itself.

Step 2: Open the hood and locate the Sensor

Once the engine is heated, open the car’s hood and locate the throttle position sensor. You might have to remove the engine cover to look for the sensor.

Step 3: Disconnect the connection

Disconnect all the wiring and connections leading to TPS to avoid getting an electric shock. Next, remove the nuts and bolts securing the TPS and gently remove it from its place.

Step 4: Clean the sensor and connector

Clean the sensor using a cleaning solution but ensure that you do not clean the actual sensor with anything liquid. Clean thoroughly around the sensor until all dirt is removed.

Step 5: Drying the Sensor

Once the sensor is cleaned, use a dry cloth and gently rub to remove any liquid residue. Then connect the sensor back in its place, close the hood and you are good to go.

Should I Repair the P0123 Trouble Code Right Away?

The P0123 code causes drivability issues and disrupts the engine’s performance and acceleration. If the problem is ignored for too long, the ECM goes into the failsafe mode and at some time the vehicle may stop completely. This is why we recommend that you get the P0123 trouble code fixed right away.

Recommended Tools to Fix P0123 Code

• Digital Multimeter
• OBD2 Scanner
• Cleaning solution
• Car battery charger

Further Questions?

If you have any further questions related to the P0123 trouble code or the throttle position sensor, just comment below and we will try to help you at. Do mention your vehicle’s model and make along with the symptoms you are facing so we can provide a solution depending on the problem.

Still have questions?

Ask any car question in our new community!

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.