P0578: Cruise control multifunction input A — input stuck — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
The monitor for cruise control multifunction input a detects an input that remains in a state that should change; this is not a statement that a mechanical actuator is necessarily seized. This is cruise control, not power steering. The named input or actuator must be matched to the vehicle diagram before interpreting the fault.
Affected system: Cruise control inputs and actuators
Symptoms
- Cruise control system fails to engage
- Cruise control system disengages unexpectedly
- Inability to adjust or set desired speed
- Cruise control indicator light remains on or flashes
- Steering wheel control buttons unresponsive
Possible causes
- Faulty cruise control steering wheel switch
- Damaged or chafed wiring in the steering column
- Corroded or loose electrical connector at the switch
- Internal failure of the cruise control module
- Intermittent electrical short to ground
What to check
- Inspect the steering wheel cruise control switch for physical damage or sticking buttons
- Check for diagnostic trouble codes in the Body Control Module or Powertrain Control Module
- Measure electrical resistance at the cruise control switch using a multimeter
- Examine the clock spring wiring harness for continuity and signs of abrasion
- Verify proper voltage and ground signals at the cruise control input circuit connector
Also written as: P0578-00, P057800, PO578 (some scan tools add the fault-type byte, e.g. -00).