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

P23D9

Cylinder 3 Fuel Heater Control Circuit Open

Per-cylinder fuel heaters (used on some heavy-duty diesels for cold-start atomisation) on cylinder 3 have an open control circuit.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number3 / D9

Possible causes

  • Open in heater or wiring high
  • Pin pushed back out of connector body low
  • Cracked solder joint inside the module or sensor low

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 80–350 €
  • Estimated time: 0.5–1.8 h
  • Component: fuel heater cyl 3
  • 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