P0585 - Cruise Control Multi-Function Input "A"/"B" Correlation

P0585 indicates a correlation error between two input signals (A and B) within the cruise control system. The Engine Control Module (ECM) or Body Control Module (BCM) monitors voltage levels from the cruise control switches. These systems typically use a resistor ladder network where each button press results in a specific voltage drop. If the signals from input 'A' and input 'B' do not correlate according to the pre-programmed logic (e.g., they show conflicting states or values outside of the allowed tolerance), the ECU flags a correlation fault. This is a safety-critical monitor to prevent unintended acceleration or failure to deactivate the system.