What it means
Cruise Control Multi-Function Input A Circuit Stuck: an electrical fault is present in the circuit. This affects cruise-control operation.
At a glance
- Usually lights the check-engine light
How it works
The cruise-control module monitors multi-function input A from the cruise buttons or stalk for commands such as set, resume, and cancel. P0578 sets when input A is detected as stuck, so a button held mechanically or an electrical signal that remains asserted can prevent normal command recognition.
Common causes
Most likely first.
- Cruise control multi-function button or stalk mechanically stuck
- Switch contacts failed
- Wiring or connector fault
- Fault in the related control module
Symptoms
- Cruise control buttons may not respond or may act as if held
- Cruise control may not engage or may stop working
- Check-engine light may come on
How to diagnose it
- Record freeze-frame data and watch input A on a scan tool while operating and releasing each cruise-control button.
- Check the multi-function button or stalk for sticking, obstruction, or damage, and confirm it returns freely after release.
- Inspect the switch connector and input A wiring for loose pins, corrosion, shorts, or chafing.
- Disconnect and test the switch according to the wiring diagram to determine whether the stuck state comes from the switch or the harness.
- If input A remains stuck with a verified switch and circuit, compare the module's input reading with the manufacturer's specification.
Common fixes
- Free or replace a mechanically stuck cruise button or stalk.
- Clean, secure, or repair a faulty switch connector.
- Repair wiring that holds input A continuously asserted.
- Replace a failed multi-function switch or stalk assembly.
- Repair or replace the related module if it reports a stuck input despite a verified circuit.
Can I keep driving?
Cruise control may fail to engage or may behave as though a command is being held. You can generally drive without cruise, but avoid using it until the stuck input is resolved.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.