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U0103 Lost Communication With Gear Shift Control Module A

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U0103 points to gear shift control module A, the electronic selector (lever, rotary knob or buttons) in shift-by-wire cars. GM's 2025 engine controllers talk to it over a LIN line and set the code as Type B once its response is absent for at least 500 ms. Stellantis calls it Electric Gear Shift Module: on the Ram 1500 (case S2208000168) U0103-00 appears with U11E3 and U1267 when the rotary selector will not leave Park, and new ESM software is the cure. Ford's Mach-E TSB 21-2405 stores U0103:87 in a secondary OBD module with a wrench lamp and Shift System Fault, fixed by reprogramming; for Explorer/Aviator, SSM 49329 blames loose grounds G210/G214. U0404 is the invalid-data sibling.

Likely causes

Selector module software fault (update available from the maker)
Loose ground or blown fuse feeding the selector
Open or shorted LIN/CAN line to the selector
Selector module internally faulty

Symptoms

  • Service Shifter or Shift System Fault message
  • Selector stuck in Park or gear changes refused
  • MIL or wrench lamp on
  • Intermittent no-crank

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–900
Time0.5–3 h

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

Parts involved

gear shift modulecan bus wiring

Related codes

U0101U0304U0404

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