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

P2B79

Coolant Heater B Control Circuit Performance

The control circuit of coolant heater B reports a control circuit performance condition. Auxiliary preheating of the coolant cannot be commanded as expected.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / numberB / 79

Possible causes

  • Heater element aged - low output high
  • Supply voltage low under load medium

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 120–600 €
  • Estimated time: 0.5–3 h
  • Component: coolant heater b
  • Component: wiring harness
  • Component: ecm
  • 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