P2123 Code: Throttle/Pedal Position Sensor/Switch “D” Circuit High

The throttle position sensor is a potentiometer or hall-effect sensor that sends an input to the powertrain control module (PCM), informing the computer about how much the driver is holding the throttle open. Meanwhile, the accelerator pedal position sensor (APP) informs the PCM about the position of the accelerator pedal on cars that have an electronic throttle actuator (TAC). If the PCM detects an issue with the throttle position (TP) sensor or accelerator pedal position sensor (APP), a P2123 code will be logged by on-board diagnostics.

What Does the P2123 Code Mean?

Diagnostic trouble code (DTC) P2123 stands for “Throttle/Pedal Position Sensor/Switch ‘D’ Circuit High.”

As the driver steps on the accelerator pedal, the APP sensor sends a reference voltage signal to the PCM and informs the computer about how much power is being requested from the engine. At the same time, the TP sensor informs the PCM about the engine’s throttle position.

Most TP sensors have two additional sensors that act as a fail-safe measure for the PCM to diagnose certain problems regarding throttle angle feedback. The same is true for the APP sensors; vehicles with TAC systems use more than one APP sensor as a fail-safe measure.

Issues with the TP or APP sensors can send the vehicle into limp mode, resulting in reduced engine performance, disabled cruise control (if applicable), or little to no response from the accelerator pedal.

Note: The definition of code P2123 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2123 Code?

• Faulty accelerator pedal position assembly with integrated APP sensors
• Bad throttle position sensor
• Throttle control motor failure
• Wiring issues
• PCM failure

What are the Common Symptoms of the P2123 Code?

• Illuminated check engine light
• Poor engine performance
• Vehicle in limp mode

How to Diagnose the P2123 Code

DTC P2123 is a generic powertrain code that can be logged in vehicles with an OBD-II system. While this might be the case, keep in mind that the steps for diagnosing this trouble code can vary, depending on vehicle specifications.

Diagnosing this trouble code typically involves using a scan tool and inspecting the affected system for any sign of damage or electrical issues. If you’re not familiar with the process, it’s a good idea to have a trained professional do the job for you instead. Otherwise, you can go ahead and do it yourself.

How to Fix the P2123 Code

Having sufficient technical knowledge of automotive repair and the right tools is crucial in resolving a trouble code like P2123. If you’re not confident with your DIY skills yet, it’s best to bring your vehicle to the nearest auto repair shop and have a certified mechanic perform the necessary repairs. This will ensure that all steps and protocols are followed correctly.

But if you think you can handle the task on your own, make sure to have the right information before proceeding. There’s no such thing as a universal solution that will resolve all trouble codes for all makes and models, so vehicle-specific information is critical in ensuring a successful repair job. You’ll find this type of information in guides like those from Chilton or an ALLDATA subscription.