P0579: Cruise Control Multi-Function Input A Circuit Range/Performance
What to do
Driveable; cruise control may respond to the wrong button or not at all. Worth asking whether the switch contacts were cleaned before a new switch pack is ordered — they are not cheap.
What this code means
The cruise control input is producing values within its electrical range but not matching any defined button. On a resistive ladder this is the classic signature of contact corrosion: the resistances have drifted enough that a pressed button falls between two defined windows, so the module can tell something was pressed but not what.
Contact cleaner and a working of the switches sometimes resolves it outright, which is worth attempting before a steering wheel switch pack is bought.
Likely causes
Start here
- Corroded switch contacts · easy
- Faulty cruise control switch · moderate
Less common
- Water ingress into connector · easy
- Faulty clock spring in steering wheel · specialist
Symptoms
Components involved
Information, not instruction
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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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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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