Code Definition

P2138 — Throttle / Pedal Position Sensor / Switch D/E Voltage Correlation

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

About P2138

P2138 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 P2138 is stored, the module has detected a correlation fault — two sensors that should track each other have diverged beyond tolerance; 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 P2138 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

The engine control module (ECM) sets P2138 when it detects a mismatch between the voltage signals from throttle/pedal position sensors 'D' and 'E.' These sensors operate in a dual-channel configuration to provide redundancy and ensure accurate throttle or accelerator pedal position readings. If the ECM finds that the signals do not correlate within a specified range, it triggers this fault as a safety measure to prevent unintended throttle operation.

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