P0578 code meaning
Cruise Control Multi-Function Input A Circuit Stuck
What P0578 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. P0578 means input A shows the same valid button voltage beyond a time limit – a button stuck. The principle matches GM's per-button codes (20 s or 89 s), here for the whole line A. No manufacturer document available to us uses this code. FCA's Jeep JK recall for the clockspring lists its own code P1593 for a stuck switch instead.
P0578 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 P0578
- Cruise control reacting unexpectedly
- Cruise control locked out
- No check engine light, engine runs normally
Common causes of P0578
- Most likelyButton mechanically stuck
- PossibleMoisture or dirt producing a constant value
- Less likelyClockspring or connector
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 P0578 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. |
| 78 | The exact fault in that area. |
What to do next
- Note P0578 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 P0578
What does P0578 mean?
P0578 means "Cruise Control Multi-Function Input A Circuit Stuck". 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 P0578?
P0578 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0578 fail an emissions test?
P0578 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 P0578 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 P0578 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.