FixItFor.Us
P codepowertrainLow severity

P0590Cruise Control Multi-Function Input "B" Circuit Stuck

The cruise control Multi-Function Input B signal is stuck at one value, as if a cruise button were being held down continuously, so the module has disabled cruise command recognition.

Definition

The module expects the Multi-Function Input B circuit to rest at its neutral voltage and change only momentarily as cruise buttons are pressed and released. P0590 sets when the signal remains fixed at one button's value for longer than plausible, for example a Set or Resume state present at key-on or held continuously while driving. Because a stuck command could otherwise cause unintended cruise behavior, the module ignores the input and cruise becomes inoperative from the affected buttons. The most common culprit is a physically sticking switch button or a shorted ladder resistor rather than wiring.

Common causes

  • Cruise button physically sticking in the switch pod (wear or spilled liquid residue)
  • Shorted or drifted resistor in the switch ladder holding a button-state voltage
  • Signal wire shorted to another circuit at a voltage matching a button state
  • Clockspring conductors partially shorted together
  • Corrosion inside the switch creating a constant resistive path

Common misdiagnoses

  • Clockspring replaced when the switch button itself is sticking
  • Control module replaced for what is a mechanical switch fault
  • Brake switch replaced because cruise is inoperative
  • Entire steering wheel harness replaced instead of the switch pod

Troubleshooting steps

  1. 1.Check the resting signal at key-on

    With no buttons pressed, view the Input B PID or back-probed voltage; if it already shows a button state, the circuit is stuck and the code is verified.

  2. 2.Press and release each button

    Confirm every button returns crisply to the neutral value when released; a value that lingers identifies the sticking function.

  3. 3.Isolate the switch

    Unplug the switch pod; if the signal immediately returns to its open-circuit voltage, the switch is at fault, and if it stays stuck the wiring or module is.

  4. 4.Measure the switch at rest

    With the pod disconnected, measure its output resistance with no buttons pressed and compare to the specified open/rest value; a low reading confirms internal sticking or shorting.

  5. 5.Verify after replacement

    Clear the code, cycle every cruise function on a road test, and confirm the stuck-input code does not return.

Related codes