OBD-II Diagnostic Trouble Code
P0578 — Cruise Control Multi-Function Input A Circuit Stuck
P0578 means one of the cruise control multi-function switch inputs (input A) is stuck. The ECM saw a cruise switch signal, such as set or resume, held active longer than expected.
Severity 2/5
Truck-relevant
Service soon
Severity
Service soon
Cruise Control Multi-Function Input A Circuit Stuck
Code
P0578
Category
Powertrain
Subsystem
Speed
Truck-relevant
Yes
What this means for truckers
P0578 (Cruise Control Multi-Function Input A Circuit Stuck) — cruise control button/switch on the steering wheel or column is stuck or wired wrong. Cruise disables. Common after winter when buttons get stuck from grime. Clean or replace control switch.
Before you replace parts — try this first
P0578 on the Speed system is most often sticking cruise switch on the steering wheel or dash — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Cruise control does not work or behaves erratically. On trucks where the same switches control PTO or engine speed, those functions may also be affected.
Common causes
- CommonSticking cruise switch on the steering wheel or dash ($100–$350)
- OccasionalFaulty clock spring on steering-wheel-mounted switches ($200–$600)
- OccasionalWiring short or damaged connector ($100–$300)
How to fix
Watch cruise switch status on a scan tool while pressing each button
When to use: First step
Clean or replace the cruise switch
When to use: When a button stays active
Check clock spring and wiring
When to use: When the switch is good
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0500 — Vehicle Speed Sensor Malfunction
- → P0501 — Vehicle Speed Sensor Range/Performance
- → P0502 — Vehicle Speed Sensor Low Input
- → P0503 — Vehicle Speed Sensor Intermittent/Erratic/High
- → P0506 — Idle Control System RPM Lower Than Expected
Frequently Asked Questions
Can I drive with code P0578?
P0578 is severity 2 — service this week. Not an immediate stop, but ignoring it usually compounds the problem. Most common cause for this code is a worn sensor or minor performance fault that won't strand you today but will get more expensive the longer you wait.
How much does it cost to fix P0578 on a commercial truck?
Total repair cost ranges $100–$600 depending on the root cause. The cheapest fix is usually the first one listed below — Sticking cruise switch on the steering wheel or dash — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0578 fail a DOT inspection?
P0578 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0578 and related codes?
P0578 is closely related to: P0500 (Vehicle Speed Sensor Malfunction), P0501 (Vehicle Speed Sensor Range/Performance), P0502 (Vehicle Speed Sensor Low Input), P0503 (Vehicle Speed Sensor Intermittent/Erratic/High). These codes share the same subsystem (speed) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0578 is set without the companions, the issue is more isolated.
How do I prevent P0578 from coming back after a repair?
For P0578 (Cruise Control Multi-Function Input A Circuit Stuck), prevention centers on the speed system. Inspect wheel speed sensor wiring at PM (rodents love it). Keep ABS tone rings clean.