A P0566 code on your 2021 Acura MDX indicates a high voltage condition in the cruise control multi-function input A circuit. High voltage suggests an open circuit condition preventing normal signal transmission.
High Voltage Interpretation
When a switch circuit shows high voltage, it typically means the signal wire is open—disconnected or broken. The ECM sees reference voltage because the switch circuit isn't completing to ground when it should be.
MDX Cruise Control Configuration
The 2021 Acura MDX features advanced cruise control with steering wheel controls. The multi-function switch combines various cruise functions. High voltage in Input A indicates that specific circuit isn't functioning.
Open Circuit Causes
The cruise control switch may have failed internally. Wiring to the specific switch circuit may be broken. Clock spring damage affects the circuit. Disconnected or corroded connectors create opens. A failed switch button prevents circuit completion.
Diagnostic Process
Use Acura HDS to monitor cruise control inputs. Press the switch button for Input A function and verify signal change. If voltage remains high regardless of switch position, the circuit is open. Test continuity from switch to ECM. Check clock spring continuity for the affected circuit.