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

P0593 Cruise Control Multi-Function Input B Circuit High

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. P0593 means signal line B is too high: GM at a ratio of 1.005–1.035 for over 2 s (short to power), FCA above 4.706 V with about 4.54 V at rest. In FCA's Jeep Wrangler JK recalls it is a typical sign of a dusty clockspring.

Likely causes

Clockspring dirty or faulty
Line B shorted to positive or ground open
Button block or connector
Module

Symptoms

  • Cruise control inoperative, possibly airbag warning (Jeep JK)
  • Cruise control locked out
  • No check engine light

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–500
Time0.5–2 h

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

Parts involved

cruise control switchclockspringswitch wiringbody control module

Related codes

P0592P0589P0591P0581P0585

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.