What it means
Same as P0564 with the analogue level inside the plausible range yet not matching any of the calibrated button levels - resistor ladder drifted, contact resistance increased, or wrong stalk module fitted.
At a glance
- Usually lights the check-engine light
How it works
The cruise-control module reads multi-function input A, often as voltage levels from a resistor network in the buttons or stalk, to distinguish commands. P0579 sets when the input is present but its level does not match any calibrated button value, so the module cannot reliably identify the requested function.
Common causes
Most likely first.
- Cruise control multi-function switch resistor network worn or drifting
- Poor contact inside the switch or stalk
- Wrong or incompatible switch assembly
- Wiring or connector fault
Symptoms
- Cruise control buttons may trigger the wrong function or respond inconsistently
- Cruise control may not engage or may stop working
- Check-engine light may come on
How to diagnose it
- Record freeze-frame data and compare live input A readings while pressing and releasing each cruise button to see whether the levels are distinct and repeatable.
- Inspect the multi-function switch or stalk for wear, contamination, damage, or a non-matching replacement assembly.
- Check the input A wiring and connectors for corrosion, loose terminals, or added resistance that could shift the signal level.
- Test the switch resistor network and harness continuity using the wiring diagram and the manufacturer's specification.
- If the switch and circuit produce correct values but the scan-tool reading is wrong, test the receiving module input.
Common fixes
- Clean and secure a high-resistance or loose switch connector.
- Repair damaged input A wiring that is changing the signal level.
- Replace a worn multi-function switch or stalk with a compatible assembly.
- Repair or replace the control module if its input reading is incorrect despite correct switch and wiring tests.
Can I keep driving?
Cruise control may not engage, or a button may trigger the wrong command, so avoid relying on it until the input readings are consistent. Normal braking and steering are generally unaffected by this cruise input fault.
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.