Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P0590 Cruise Control Multi-Function Input B Circuit Stuck

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Cruise control buttons form a resistor ladder on one or two signal lines, each button giving its own voltage window. FCA uses two lines with offset windows – signal 1 is input A, signal 2 input B – and both must report the same button; GM evaluates the ratio to the reference. Any fault locks out cruise control; CARB treats this as emission-neutral, and GM and Ford set these codes without warning lamp. P0590 means input B reports a pressed button permanently – a button stuck or a voltage hanging in one window. No manufacturer document available to us uses P0590; FCA reports a stuck button with its own code P1593 or with P0585, and GM has no stuck code for input B. Counterpart of P0578 for input A.

Likely causes

Button stuck mechanically (trim, dirt, spilled drink)
Short in the button block's resistor ladder
Moisture or corrosion in the switch
Module

Symptoms

  • Cruise control cannot be engaged, button noticeably sticking
  • Cruise control locked out
  • No check engine light

Repair estimate

DifficultyEasyWorkshop job
Parts and labour€0–350
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

cruise control switchclockspringswitch wiringbody control module

Related codes

P0578P0585P0589P0591P0592P0593

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com.