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

P2605

Intake Air Heater B Circuit / Open

The controller cannot drive the secondary intake air heater (heater grid B) used on diesel engines for cold-start support. The grid stays cold so cold-start emissions and white smoke increase.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number6 / 05

Possible causes

  • Open heater grid element high
  • Failed heater relay or open coil medium

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 120–600 €
  • Estimated time: 0.8–2.5 h
  • Component: intake air heater b
  • Component: heater relay
  • Component: wiring harness
  • 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