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P codepowertrainLow severity

P0564Cruise Control Multi-Function Input "A" Circuit

The PCM sees an implausible or faulted signal from the cruise control multi-function input circuit that carries the steering-wheel switch commands.

Definition

Many vehicles run all cruise control switch commands (On/Off, Set, Resume, Cancel) into the PCM or cruise module on a single multiplexed circuit, where each button produces a distinct voltage through a resistor ladder. P0564 sets when the voltage on this "A" circuit is out of range, stuck, or does not match any valid button state — commonly from a sticking switch, clockspring wear, or wiring faults. Cruise control is disabled as a fail-safe and typically will not engage; the MIL may or may not illuminate since this is a convenience system, but on some vehicles the cruise indicator flashes.

Common causes

  • Worn or sticking steering-wheel cruise switch changing the circuit resistance
  • Damaged clockspring (spiral cable) in the steering column
  • Chafed or shorted wiring between the switch and PCM
  • Corrosion in the switch or column connectors
  • Spilled liquid inside the switch assembly
  • Faulty PCM input circuit (rare)

Common misdiagnoses

  • PCM or cruise module replaced when the switch resistance has drifted
  • Brake light switch replaced when the multi-function input is at fault
  • Entire steering wheel switch pack replaced when only the clockspring is worn
  • Throttle body replaced for cruise-inoperative complaints

Troubleshooting steps

  1. 1.Monitor the switch input on a scan tool

    Watch the cruise switch status or voltage PID while pressing each button; every command should register distinctly, and a stuck or invalid state identifies the fault.

  2. 2.Measure the resistor-ladder values

    Disconnect the switch and measure resistance for each button press against the service chart; out-of-spec or erratic values condemn the switch.

  3. 3.Test through the clockspring

    Check circuit continuity from the column connector while turning the steering wheel lock to lock; resistance changes with wheel angle indicate a failing clockspring.

  4. 4.Inspect wiring to the PCM

    Verify the signal wire is not open, shorted to ground, or shorted to voltage between the column base and the PCM connector.

  5. 5.Verify operation after repair

    Clear the code and road test, confirming Set, Resume, Cancel, and Off all function and the code does not return.

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