Network, generic

U0102 Lost Communication With Transfer Case Control Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0102 is logged when the transfer case control module, which shifts between two- and four-wheel drive and between high and low range, stops sending. GM's 2025 engine controllers expect frame $035 and fail it when gaps exceed 425 ms within a 5 s window; the code is Type C, emissions-neutral and without MIL. The earlier two-mode hybrid trucks (2012 table) used Type B with 500 ms detection between 10 and 18 V. Ford's 2023 diesel controllers allow 5 s before flagging the TCCM. Bulletin 08-07-30-021H lists U0102 among GMLAN codes caused by shared bus faults. The driver mostly sees a 4WD warning and a transfer case left in its last range; engine and gearbox keep running. U0403 covers implausible data from the same module.

Likely causes

Transfer case module without power or ground
Water or corrosion in the module connector (often mounted low on the frame)
Damaged CAN lines to the transfer case module
Transfer case module internally faulty

Symptoms

  • 4WD or AWD warning, range selection ignored
  • Transfer case stays in its last mode
  • Usually no MIL

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–900
Time0.5–3 h

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

Parts involved

transfer case control modulecan bus wiring

Related codes

U0073U0303U0403U0114

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