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P0592Cruise Control Multi-Function Input "B" Circuit Low

The cruise control Multi-Function Input B circuit is stuck near zero volts, indicating the signal line is shorted to ground, and cruise commands from the affected buttons are ignored.

Definition

The Multi-Function Input B circuit normally rests at a reference voltage supplied through the module's pull-up, with each cruise button pulling it to a distinct lower value through the switch's resistor ladder. P0592 sets when the module sees the circuit at or near ground continuously, a state no valid button combination can produce, which indicates a short to ground in the switch, clockspring, or wiring. The module disables cruise input recognition while the fault is present, so cruise will not set or resume. Engine operation is unaffected and the MIL usually does not illuminate.

Common causes

  • Signal wire chafed to ground in the steering column or dash harness
  • Internally shorted cruise switch pulling the ladder to near zero ohms
  • Clockspring conductor shorted to its ground circuit
  • Crushed harness from prior steering column or airbag service
  • Moisture bridging the signal terminal to ground in a connector

Common misdiagnoses

  • Switch pod replaced when the harness short is downstream of it
  • Control module replaced without disconnecting the circuit to isolate the short
  • Brake switch replaced for an input-circuit code
  • Clockspring replaced when the short is at the column base connector

Troubleshooting steps

  1. 1.Confirm the stuck-low state

    Back-probe the Input B circuit at the module with the key on; a constant reading near 0 volts instead of the pull-up reference verifies the fault.

  2. 2.Unplug the switch pod

    If the voltage recovers to the open-circuit reference with the switch disconnected, replace the switch; if it stays low, the short is in the wiring.

  3. 3.Sectionalize the harness

    Disconnect the clockspring lower connector next; recovery there condemns the clockspring, while a still-low signal points to the column-to-module harness.

  4. 4.Ohm the wire to ground

    With both ends disconnected, measure the signal wire to chassis ground and trace the run for the chafe or crush point where continuity exists.

  5. 5.Repair and retest

    Repair the insulation or terminal, verify the resting reference voltage returns, and confirm all cruise buttons decode correctly on the scan tool.

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