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U0028 Generic (SAE) Basic entry

Vehicle Communication Bus A

Updated 2026-10-02 · Network communication (generic)

Severity
Medium
Typical repair cost
50 – 700 EUR
System
Network

What it means

U0028 indicates a fault on the vehicle communication bus itself rather than in one component: Vehicle Communication Bus A. Several modules may log related codes at the same time.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

  • Several warning lights on at the same time
  • Functions controlled by the affected module do not work
  • Scan tool cannot communicate with one module
  • Gauges dropping to zero or dashboard flickering

Common causes

  1. Blown fuse or no power supply to the Vehicle Communication Bus A
  2. Poor ground for the module
  3. Damaged CAN/data bus wiring or connector
  4. Failed module
  5. Low battery voltage during cranking or after a jump start

How to diagnose

  1. Check which modules respond to a full system scan and which do not
  2. Verify fuses, power and ground at the Vehicle Communication Bus A connector
  3. Measure CAN bus resistance between the two bus wires (about 60 ohms with the battery disconnected) and inspect the wiring
  4. Check battery voltage and charging system; low voltage causes many communication codes
  5. Replace or reprogram the module only after power, ground and bus wiring are confirmed

Frequently asked questions

Can I keep driving with U0028?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing U0028 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

U0026U0027U0029U0030

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