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P0577Cruise Control Input Circuit High

The cruise control input circuit is reading a voltage higher than the expected range, usually from an open circuit or short to voltage.

Definition

The PCM or cruise module reads a voltage-coded signal from the cruise switch circuit and expects it to sit at a defined level for each switch state. P0577 sets when the signal stays above the maximum plausible voltage, which typically indicates an open circuit — a broken wire, failed clockspring, or unplugged switch — or a short to battery voltage. Cruise control is disabled and will not engage; the fault has no effect on driveability or emissions and normally does not illuminate the MIL.

Common causes

  • Open circuit in the cruise switch signal wire or its ground return
  • Failed clockspring breaking continuity through the steering column
  • Disconnected, corroded, or backed-out terminal at the switch or module connector
  • Failed cruise switch with an internally open resistor ladder
  • Signal wire shorted to a voltage feed
  • Faulty module input circuit (rare)

Common misdiagnoses

  • Replacing the cruise switch when the clockspring is open
  • Replacing the brake light switch
  • Replacing the PCM for a simple broken wire
  • Replacing the cruise servo/actuator

Troubleshooting steps

  1. 1.Measure the input voltage at the module

    With the key on, a signal pegged at reference or battery voltage regardless of button presses confirms an open or short to voltage.

  2. 2.Test the circuit end to end

    Disconnect the switch and module connectors and check continuity of the signal and ground wires; more than about 1 ohm or an open reading fails the harness.

  3. 3.Check the clockspring continuity

    Measure through the spiral cable while turning the wheel; intermittent opens with steering movement are a classic clockspring failure.

  4. 4.Ohm the cruise switch

    Verify each button produces its specified resistance; an open in all positions means a failed switch or broken switch ground.

  5. 5.Verify and road test

    Repair the open, confirm correct voltage steps for every button, clear the code, and confirm cruise engages on a road test.

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