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U0404 Invalid Data Received From Gear Shift Control Module A

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Gear shift control module A is the electronic selector of shift-by-wire cars: lever, dial or buttons that report the chosen range as data. U0404 means its messages still arrive but the receiver, usually the transmission controller, rejects them. GM's 2025 ECM checks counter and protection fields of the selector's position-sensor and self-check signals, fails a signal after 4 errors in 10 or 8 in 18 checks; the code is Type B with two trips. FCA stored U0404 in the TCM of 2016 Durango and Grand Cherokee eight-speeds with MIL and a blinking M on shifter and cluster, cured by TCM software (21-011-16 Rev. A). Audi found U040400 in the gearbox unit of 2021 A6/A7 models with an intermittent selector lever fault message and no range selectable; the gateway J533 needed new software. U0103 means lost contact, U0304 a software conflict.

Likely causes

Software of TCM or gateway (update available)
Position sensor or electronics in the selector delivering implausible values
Connector or bus line at the selector loose or corroded
Gear shift module internally faulty

Symptoms

  • Selector fault message or flashing range indicator
  • Range cannot be selected or vehicle stays in Park
  • Check engine light

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,200
Time0.3–2.5 h

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

Parts involved

gear shift modulecan bus wiring

Related codes

U0103U0304U0592U0402

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