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

U0012

Medium Speed CAN Communication Bus (-) Open

The CAN-Low wire on the medium-speed comfort/body bus is open. Body modules such as door modules, climate control or seat modules lose communication, but powertrain functions usually stay alive.

SystemNetwork
Typegeneric / SAE
GroupU0
Range / number– / 12

Possible causes

  • CAN-Low wire broken in body harness high
  • Loose body control module connector 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: 60–500 €
  • Estimated time: 0.8–4 h
  • Component: can low wire
  • Component: body 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