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

U0003

High Speed CAN Communication Bus (+) Open

The CAN-High line of the high-speed bus is open. Without the differential pair, the controller cannot decode any traffic and reports loss of all participating modules at once. Often follows a wiring repair, accident damage, or a corroded connector pin.

SystemNetwork
Typegeneric / SAE
GroupU0
Range / number– / 03

Possible causes

  • CAN-High wire broken or pin pushed back high
  • Corroded module connector medium
  • Harness damage after repair or accident medium

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: 80–800 €
  • Estimated time: 1–6 h
  • Component: can high wire
  • Component: module connector
  • Component: can transceiver
  • MIL / check engine light
  • limp mode possible

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