Code Definition

P0579 — Cruise Control Multi-Function Input A Circuit Range/Performance

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

About P0579

P0579 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 P0579 is stored, the module has detected a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour.

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 P0579 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 several switch functions on one 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 decodes. Each valid function occupies a narrow voltage window, with deliberate dead bands between the windows so the module can distinguish one button from another with confidence. DTC P0579 sets when the ECM measures a voltage on input A that lies within the overall operating range but falls into one of those dead bands bet...

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