P0578–P0590 Cruise Control Multi-Function Input A Circuit Stuck
The part is not moving as commanded - physically stuck rather than electrically dead.
Can you drive it? The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
P0578 | Cruise Control Multi-Function Input A Circuit Stuck | Investigate soon |
P0590 | Cruise Control Multi-Function Input B Circuit Stuck | Investigate soon |
The definition
P0578: Cruise Control Multi-Function Input A Circuit Stuck.
P0578 is a powertrain code (the engine or gearbox), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.
What to check first
Cheapest and fastest checks first:
- Check the part can move by hand with the engine off, where it is safe to do so.
- Look for carbon or soot build-up, which is the usual reason a flap or valve stops moving on these engines.
What actually causes this on a VAG
Official definition: Cruise Control Multi-Function Input "A" Circuit Stuck. On VW, Audi, SEAT and Skoda the cruise controls sit on a stalk on the steering column (on the newest models they are buttons on the steering wheel instead). "Stuck" means the car keeps reading one of those controls as pressed when nobody is touching it. Because the system will not engage while it thinks a control is jammed, the usual symptom is simply that cruise control stops working. Nothing about the engine itself is wrong, and refusing to engage is the safe behaviour - but if the car ever behaves as though cruise is active when you have not set it, stop using cruise and get it looked at before driving further. One thing worth knowing before anyone starts: on most VAG models from the mid-2000s onward the stalk does not wire straight to the engine ECU. It plugs into the steering column electronics module, which passes the button states on to the engine. So the useful detail is often not in the engine ECU at all - have the steering column electronics module (address 16) scanned too, where VAG describes the same fault in plain language, along the lines of "turn signal switch - cruise control system button - implausible signal".
Most likely causes, in order
- Moisture or dirt inside the cruise stalk. The stalk contacts sit in the steering column where spilled drinks and general grime end up, and the contacts wear with age. Damp or dirty contacts can bridge and hold a button 'on'. This is the most common cause and the cheapest to confirm: a scan tool's live data for the cruise switch will show the stuck state with the stalk untouched. That one check confirms it before anything is bought.
- Corroded, damp or unseated connector at the base of the steering column. The stalk plugs into the column electronics behind the shroud. Green, wet or half-seated pins there produce exactly the same 'permanently pressed' reading as a bad stalk, and it is far cheaper to fix. Check for water in the driver's footwell or a blocked scuttle/pollen-filter drain at the same time, as those are a common source of the damp.
- The steering column electronics module itself, or its coding. On models where the stalk reports through that module, a water-damaged or failed module - or one that has been swapped, or left un-coded after a stalk change - can report switch states that were never sent. Scan address 16: if the fault is stored there against the cruise buttons and the stalk and its plug check out clean on live data, the module is the suspect rather than the stalk.
- Wrong-variant or badly retrofitted cruise stalk. On older VW, Audi, SEAT and Skoda models - broadly late 1990s to early 2010s - cruise control was a very common retrofit. Fitting a stalk from a different model, or coding the car for cruise without the matching stalk, gives switch readings the car cannot make sense of. If the car has recently had a stalk fitted, or the fault appeared right after a retrofit, check the part variant and the coding before anything else.
Worth knowing: Before anyone removes the column shrouds, have the cruise switch's live value watched with the stalk untouched, then with each button pressed. That one check separates a genuinely stuck stalk from a wiring or module problem, and it stops you paying for a stalk when the real fault is a damp plug. Two more things worth doing first, both free. If a brake light switch fault is stored alongside this one, deal with that first - a faulty brake switch disables cruise on these cars, VAG's own fault text pairs the two, and the switch is a cheap and very common failure. And if you are going behind the shrouds yourself, remember the airbag and its clock spring are right there: disconnect the battery and leave it standing for the time the manufacturer specifies before disturbing anything with a yellow connector, or leave that part to a workshop. The live-data check needs none of that.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
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Common questions
What does P0578 mean?
P0578 means Cruise Control Multi-Function Input A Circuit Stuck. The part is not moving as commanded - physically stuck rather than electrically dead.
Can I drive with P0578?
The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.