DTC C1669-83: CAN Message Failure - ACU: General Description
WARNING: This page is about a different car, the 2024 Kia Sorento. However, it is still accessible from the selected car via links, so may be relevant.
The IEB module is composed of a Electronic Control Unit (ECU) and an Hydraulic Control Unit (HCU), so the IEB module hardware includes all solenoid valves inside the unit as well as the ECU.
Solenoid valves are switched to "ON", "OFF" by IEB module when the ABS is activated. Solenoid valves function is to increase, decrease or maintain the hydraulic pressure supplied to a wheel cylinder.