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U0403 Invalid Data Received From Transfer Case Control Module

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

U0403 points to data from the transfer case control module, the unit that engages four-wheel drive and selects the range: its frames keep coming, yet the listener rejects what they carry. In GM's 2025 tables the ECM watches the secondary-axle signals from this module for faulty rolling counter, protection value or checksum, needs 8 bad results out of 18 to fail and assigns Type B (MIL on the second trip), whereas the lost-contact code U0102 there is Type C. On 2014-2016 Silverado, Sierra, Tahoe and Escalade GM saw U0403 with a Service 4WD message when ignition 1 voltage dropped out at fuse block terminals (PIT5391A). On 2019-2020 Ram 1500 with electronic transfer cases, U0403 and U1440 with traction lamp, driveline bumps and motor clicking were fixed by new drivetrain module software (08-083-20). U0303 is a software conflict.

Likely causes

Software of the transfer case or drivetrain control module (update available)
Ignition voltage dropping out at fuse block terminals or relays
Faulty range position sensor making the module send implausible values
Transfer case control module internally faulty

Symptoms

  • Service 4WD message
  • Traction control or check engine light on
  • Driveline bumps or clicking from the transfer case motor

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,200
Time0.3–3 h

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

Parts involved

transfer case control modulecan bus wiring

Related codes

U0102U0303U0400

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