Network, generic

U0104 Lost Communication With Cruise Control Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0104 names the cruise control module, today usually the radar unit of adaptive cruise control that sends speed and distance requests to the engine. GM's 2019 truck ECMs check its frames $2CB and $2CD, treat gaps beyond 500 ms that persist for 3 s as a failure and classify the result as Type C, emissions-neutral and without MIL; detection pauses while the bus-off code of the carrying bus (U0073, U0074) is active. Saab's 2011 9-4x code list carries U0104 with sub-codes for short to ground, invalid data, wrong message counter and checksum error. While the code is active, cruise or distance control switches off or cannot be armed; driving and emissions are unaffected. U0405 covers implausible data from this module.

Likely causes

Radar/cruise module without power or with a wet, loose connector (front bumper area)
Front-end damage or bumper repair affecting module or wiring
Damaged CAN lines to the module
Cruise/radar module internally faulty

Symptoms

  • Cruise or adaptive cruise unavailable, warning message
  • Forward collision alert may switch off as well
  • No MIL

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,500
Time0.5–3 h

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

Parts involved

cruise control modulecan bus wiring

Related codes

U0073U0074U0305U0405

References: gsi.ext.gm.com, saabwisonline.com, en.wikipedia.org.