P0578: Cruise Control Multi-Function Input A Circuit Stuck
What to do
Driveable; cruise control will refuse to engage, which is the system protecting itself from a stuck button. Do not attempt to use cruise control until it is repaired.
What this code means
One of the cruise control inputs is reading as permanently pressed. The module detects this by noting that a button has been held far longer than any person would hold it, and refuses to act on it — which is the correct response and is why the practical consequence is cruise control that will not engage rather than one that behaves unpredictably.
A stuck switch and a water-bridged contact are the usual causes, and drying the assembly is worth trying before replacement.
Likely causes
Start here
- Faulty cruise control switch · moderate
- Water ingress into connector · easy
Less common
- Signal wire shorted to ground · moderate
- Faulty clock spring in steering wheel · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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