Code Definition

P2123 — Throttle / Pedal Position Sensor / Switch D Circuit High Input

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Toyota

About P2123

P2123 is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Toyota vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P2123 is stored, the module has detected a signal or supply voltage higher than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P2123 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

Accelerator pedal position sensor D is one of the redundant sensors that report driver pedal demand to the engine control module in a drive by wire system. The module supplies a regulated reference voltage and expects the returned signal to sit at a defined low value with the pedal released, rising smoothly and proportionally as the pedal is pressed. DTC P2123 sets when the module measures that signal above the maximum valid threshold, commonly over about 4.8V, which indicates a short to a voltage source, an open sensor ground allowing the input to float high, or a failed sensor stuck at full ...

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