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

P0585 Cruise Control Multi-Function Input A/B Correlation

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. P0585 means inputs A and B contradict each other although both voltages are valid – one reports a button, the other rest or another button. Documented only by FCA: a 2022 bulletin traces it to a SET+ button stuck by a badly seated trim, another names oxidised steering wheel contacts. FCA gives no thresholds; GM does not use P0585.

Likely causes

Button stuck mechanically (trim, dirt)
Increased contact resistance on one line (clockspring or column module connector)
Button block faulty internally
Clockspring faulty

Symptoms

  • Cruise control not engaging or cutting out, button sticking
  • Cruise control locked out
  • No check engine light

Repair estimate

DifficultyEasyWorkshop job
Parts and labour€0–400
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

P0578P0579P0590P0591P0580P0592

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.