Code P2138 indicates that the engine control module has detected a voltage correlation fault between the two throttle position sensor circuits (or between the two accelerator pedal position sensor circuits). These redundant sensors are designed to output proportional voltages that track each other; when their signals diverge beyond a calibrated threshold, the ECM sets this code and typically forces a reduced-power operating mode.
One of the redundant sensor elements has drifted out of specification or developed an internal open/short, causing the two signal voltages to disagree.
Chafed, corroded, or broken wires — or loose/pitted connector terminals — create resistance differences that skew one signal relative to the other.
A shared 5 V reference or ground path that is high-resistance or interrupted affects the two sensor outputs unequally.
Carbon buildup, broken return spring, or worn pivot points cause the physical position to differ from the ECM's expected correlation.
Rare; an internal ADC or signal-processing failure can misread otherwise valid sensor signals. Consider only after all wiring and sensor tests pass.
The vehicle will likely enter a reduced-power limp mode, making highway driving unsafe. Have it diagnosed promptly.
No. The fault can originate in the accelerator pedal assembly, the wiring between either sensor and the ECM, or the shared reference/ground circuits.
Many vehicles require a throttle position relearn or idle adaptation procedure after sensor replacement; consult the service information for the specific model.
ECM failure is very rare for this code. Wiring, connectors, or the sensors themselves are responsible in the vast majority of cases.