P0638 Throttle Actuator Control Range/Performance (Bank 1)

P0638 indicates throttle actuator control range or performance on Bank 1. The commanded throttle movement does not match the expected position or response for Bank 1.

Code details

Generic OBD-II · P0

System: Computer
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the throttle body before checking wiring, pedal data, carbon buildup, and required throttle relearn procedures.

Symptoms of P0638

Check-engine light, sometimes with several unrelated codes at once.
Warning lights, a no-start, or intermittent electrical faults.
Communication or module-reset problems on a scan tool.

Common causes of P0638

Low battery voltage, poor grounds, corroded connectors, or blown fuses.
Wiring or network (CAN bus) faults between modules.
A module software/programming issue, or rarely a failed controller.

Useful checks before replacing parts

Compare commanded throttle position, actual throttle position, accelerator pedal data, idle speed, airflow, freeze-frame load, and related TAC codes.
Inspect throttle body deposits, actuator movement, wiring, connector terminals, reference voltage, grounds, intake restriction, and PCM driver control.
Command the throttle through a scan tool or relearn procedure and verify smooth movement without sticking, lag, or disagreement.

Related OBD-II codes

These nearby computer entries can help compare wording and pin down the fault area.