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P0589Cruise Control Multi-Function Input "B" Circuit

A general fault has been detected on the cruise control Multi-Function Input B circuit, the second multiplexed signal line that carries the steering-wheel cruise button commands to the module.

Definition

Cruise control switch pods typically encode each button (On/Off, Set, Resume, Cancel) as a distinct voltage on a resistor-ladder signal circuit, and many systems carry a second such circuit, Input B, for redundancy or additional functions. The module continuously reads this input and sets P0589 when the voltage does not correspond to any valid switch state or the circuit behaves erratically. With the fault active the module ignores or limits cruise commands, so cruise may not set, resume, or cancel from the wheel buttons. There is no driveability impact and the MIL normally does not illuminate for this code.

Common causes

  • Faulty steering-wheel cruise switch with a damaged resistor ladder
  • Worn or broken clockspring circuit for the Input B signal
  • Corroded or intermittent connector in the steering column
  • Chafed signal wire between the column and the control module
  • Liquid intrusion into the switch pod altering the ladder resistances
  • Control module input circuit fault

Common misdiagnoses

  • Clockspring replaced when the switch pod itself is out of spec
  • Brake pedal switch replaced because cruise will not engage
  • Cruise servo or actuator replaced for an input-side signal fault
  • Control module replaced before the switch voltages are measured

Troubleshooting steps

  1. 1.Watch the input on a scan tool

    Display the Multi-Function Input B PID (voltage or decoded button state) while pressing each cruise button and confirm each press produces its expected, stable value.

  2. 2.Measure the switch resistor ladder

    Disconnect the switch pod and verify each button produces the resistance listed in service data; an erratic or out-of-range step means a failed switch.

  3. 3.Verify the clockspring path

    Check continuity through the clockspring on the Input B circuit while rotating the wheel slowly lock to lock, watching for dropouts.

  4. 4.Back-probe at the module

    Measure the Input B voltage at the module connector while pressing buttons to determine whether the fault is upstream wiring or the module itself.

  5. 5.Inspect for contamination

    Open the switch area and column connectors and look for drink spills, corrosion, or damaged terminals.

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