P0579 code meaning
Cruise Control Multi-Function Input A Circuit Range/Performance
What P0579 means
Cruise control buttons are almost always a resistor ladder on one or two signal lines, each button giving its own voltage; the module reading it (GM and Saab from about 2010: the body module; FCA: steering column module or PCM) sends the button state to the engine module over CAN. CARB names cruise control as the example of an emission-neutral diagnosis – it is simply switched off – so GM lists all these codes as type C and Ford as non-MIL: no warning lamp, the engine runs normally. FCA uses two redundant lines with mirrored ladders: P0579 sets when signal 1 is outside its window while a button is pressed – for on/off it must lie between 0.235 and 0.353 V – and is active only while the button is held. Usual cause is oxidation at the six-pin steering wheel connector or the clockspring; the Jeep JK recall replaces the clockspring.
P0579 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0579
- Cruise control cannot be switched on at times
- Cruise control locked out
- No check engine light, engine runs normally
Common causes of P0579
- Most likelyOxidised or dirty contacts at the steering wheel connector
- PossibleSwitch contact for signal 1 not closing
- PossibleClockspring faulty
- Less likelyWiring or module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cruise control switchClockspringSwitch wiringBody control module
What each part of P0579 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 79 | The exact fault in that area. |
What to do next
- Note P0579 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0579
What does P0579 mean?
P0579 means "Cruise Control Multi-Function Input A Circuit Range/Performance". Cruise control buttons are almost always a resistor ladder on one or two signal lines, each button giving its own voltage; the module reading it (GM and Saab from about 2010: the body module; FCA: steering column module or PCM) sends the button state to the engine module over CAN. It is a generic code, so it means the same on every make.
Is it safe to drive with P0579?
P0579 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0579 fail an emissions test?
P0579 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0579 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0579 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.