Network, generic (extended)

U3028 Control Module A Disable Feedback Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

A disable line is only useful if someone can prove it works, so many designs read back what actually arrives at the switched module. U3028 reports a fault in that feedback path for module A: the returned signal is missing or does not match the state that was commanded. GM's patent US9122662B2 shows the principle: while the ignition is off, several processors set their outputs in a fixed series of test states and compare the resulting output of the inhibit path with the expected value, flagging a fault on any mismatch. FCA's patent US10676100B2 likewise steps through six combinations of shutoff signals. No manufacturer documents U3028 publicly. Unlike U3025, the shutdown line itself may be fine; the system just cannot confirm it, so it often withholds the function until a test passes.

Likely causes

Open feedback wire or loose pin between module A and the monitoring module
Self-test disturbed by low voltage or an early shutdown
Faulty readback stage in module A or the monitoring module

Symptoms

  • Function of module A blocked after the self-test, system warning
  • Fault may appear only at start-up or shutdown

Repair estimate

DifficultyHardWorkshop job
Parts and labour€50–1,200
Time1–4 h

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

Parts involved

module disable feedback afeedback wiring

Related codes

U3029U302AU3025

References: law.cornell.edu, patents.google.com, patents.google.com.