Code U0105 on the 2021 Hyundai Sonata indicates lost communication with the throttle actuator control module. This module manages the electronic throttle body, translating accelerator pedal inputs into throttle plate position for precise engine air flow control.
Electronic Throttle Control
The Sonata uses drive-by-wire throttle control - there's no physical cable connecting the accelerator pedal to the throttle. Instead, the accelerator pedal sensor sends signals to the ECM/TAC module, which then positions the throttle plate electronically. Communication failure interrupts this critical control loop.
Symptom Severity
With U0105 active, the engine may enter a reduced power mode or refuse to start. If running, acceleration response may be severely limited or erratic. The check engine light and potentially other warnings illuminate. This code affects basic vehicle drivability significantly more than many other communication faults.
Diagnostic Focus
On many vehicles, the TAC function is integrated into the ECM rather than being a separate module. Verify your Sonata's configuration using service information. Check throttle body connections, accelerator pedal position sensor signals, and ECM communication. A faulty throttle body motor or position sensor can cause communication-related codes.
Repair Requirements
Address wiring and connector issues first. If the throttle body requires replacement, throttle relearn procedures are necessary after installation. If an actual TAC module exists separately and has failed, replacement requires programming with Hyundai GDS equipment.