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!

Powertrain generic / SAE

P28C1

Ion Sense Module Supply Voltage Low

Supply voltage on the ion sense module is below the expected window. Wiring shorted to ground, blown fuse, or upstream regulator fault.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number8 / C1

Possible causes

  • Module supply fuse blown high
  • Supply wire shorted to ground medium

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 100–600 €
  • Estimated time: 0.5–3 h
  • Component: ion sense module
  • Component: wiring harness
  • MIL / check engine light
  • emissions-relevant

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