P0123

P0123 is a diagnostic trouble code (DTC) that may be logged by a vehicle's engine control module (ECM) or powertrain control module (PCM). This particular code indicates a problem with the throttle position sensor (TPS) circuit. Specifically, it often signifies a "Throttle Position Sensor/Switch A Circuit High" issue. The TPS is a crucial component that tells the ECM how far the throttle pedal is depressed, which in turn affects engine performance, fuel delivery, and transmission shifting.

When P0123 is triggered, it means the voltage signal from the TPS circuit is higher than the ECM expects. This can be caused by several factors. A common culprit is a faulty TPS itself, which may be sending an incorrect signal due to internal wear or damage. Wiring issues are also frequent causes, including short circuits to voltage, damaged insulation, or loose connections within the TPS connector or the wiring harness leading to the ECM. Additionally, problems with the ECM itself, though less common, can also lead to this DTC being set.

The symptoms associated with P0123 can vary but often include a check engine light illuminating on the dashboard, rough idling, poor acceleration, stalling, or the vehicle entering a "limp mode" where engine power is significantly reduced to prevent further damage. Diagnosis typically involves checking for voltage readings at the TPS connector and inspecting the wiring for any signs of damage. Replacing the TPS or repairing faulty wiring are common solutions.