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 or reserved

U300A

Ignition Switch

The control module detects an inconsistent or implausible ignition switch state — multiple positions reported simultaneously, or the position contradicts other inputs.

SystemNetwork
Typegeneric or reserved
GroupU3
Range / number– / 0A

Possible causes

  • Ignition switch contacts worn high
  • Gateway module routing CAN messages incorrectly low
  • CAN terminating resistor (120 Ω) drifted out of spec 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: medium
  • DIY: possible
  • Estimated cost: 60–400 €
  • Estimated time: 0.5–2 h
  • Component: ignition switch
  • Component: ignition wiring
  • 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