OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Network generic / SAE

U0028

Vehicle Communication Bus A

Generic fault on vehicle communication bus A. The controller flags an unspecified electrical or protocol fault on this bus segment that does not match the more specific U0xxx subcodes.

SystemNetwork
Typegeneric / SAE
GroupU0
Range / number– / 28

Possible causes

  • Intermittent CAN wiring fault high
  • Marginal node corrupting traffic medium
  • Gateway module routing CAN messages incorrectly low

Symptoms

  • Multiple warning lights may illuminate
  • Affected modules may go into limp mode or shut down
  • Specific functions inoperative depending on module
  • Diagnostic tools may show communication faults

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 80–700 €
  • Estimated time: 1–5 h
  • Component: can bus wiring
  • Component: control module
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication