Code Definition

P0578 — Cruise Control Multi-Function Input A Circuit Stuck

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0578

P0578 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0578 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0578 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The cruise control multi function input A circuit carries the state of several switch functions on a single wire using a resistive ladder, where set, resume, accelerate, coast, and cancel each place a distinct resistance into the circuit to produce a unique voltage the Engine Control Module can decode. The module monitors how long any given switch state persists and compares it against a plausibility timer, because a driver cannot realistically hold a cruise button for an extended period. DTC P0578 sets when the ECM sees input A remaining at one valid switch voltage continuously beyond that ca...

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