C1646Signal from the transmission computer (TCM) missing or invalid (CAN)

• Hyundai/Kia code · Power steering
• Lights a warning lamp

How the car detects it

The power steering unit doesn't get valid data from the transmission computer (TCM) over CAN; it uses engine and speed data to decide how much to assist. When the power steering limits or stops its assistance, the steering becomes heavy but still works mechanically.

What you may notice

• Power steering warning light

Likely causes

• LikelyCAN wiring or connectors
• PossiblePower or ground of the transmission computer (TCM)

Sources

• static.nhtsa.gov › MC-10179244-0001.pdf · official document

Backed by an official manufacturer document.

From Obdaryn's Hyundai/Kia pack, exactly as the app shows it, with the public sources above. Guidance only; confirm with a workshop.