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

P0579 Cruise Control Multi-Function Input A Circuit Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Cruise control buttons are almost always a resistor ladder on one or two signal lines, each button giving its own voltage; the module reading it (GM and Saab from about 2010: the body module; FCA: steering column module or PCM) sends the button state to the engine module over CAN. CARB names cruise control as the example of an emission-neutral diagnosis – it is simply switched off – so GM lists all these codes as type C and Ford as non-MIL: no warning lamp, the engine runs normally. FCA uses two redundant lines with mirrored ladders: P0579 sets when signal 1 is outside its window while a button is pressed – for on/off it must lie between 0.235 and 0.353 V – and is active only while the button is held. Usual cause is oxidation at the six-pin steering wheel connector or the clockspring; the Jeep JK recall replaces the clockspring.

Likely causes

Oxidised or dirty contacts at the steering wheel connector
Switch contact for signal 1 not closing
Clockspring faulty
Wiring or module

Symptoms

  • Cruise control cannot be switched on at times
  • Cruise control locked out
  • No check engine light, engine runs normally

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–500
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

P0578P0580P0581P0585P0591P0564

References: static.nhtsa.gov, static.nhtsa.gov, roushcleantech.com.