Code Definition

P0591 — Cruise control multifunction switch signal out of range - Circuit B

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

About P0591

P0591 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 P0591 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 P0591 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

This fault code signifies that the engine control module (ECM) or the body control module (BCM) has detected a signal from Circuit B of the cruise control multifunction switch that is outside the expected range. The multifunction switch is essential in the operation of the cruise control system, enabling the driver to engage, set, adjust, and disengage cruise control. An out-of-range signal in Circuit B can indicate an electrical issue such as a faulty switch, wiring problem, or an incompatible signal, leading to erratic or non-functional cruise control behaviour.

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