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

P2AB1

Catalyst Heater Control Module Performance

The ECM detects that the catalyst heater control module does not respond to commands within the expected window. Heating output is reduced or absent during catalyst light-off.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / numberA / B1

Possible causes

  • Internal control module fault high
  • Communication with ECM degraded medium
  • Module software outdated, reflash may resolve low

Symptoms

  • Check engine light on
  • Failed emissions inspection
  • Possibly slightly increased fuel consumption
  • Sulfur (rotten egg) smell from exhaust under load

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 400–2000 €
  • Estimated time: 2–6 h
  • Component: catalyst heater module
  • Component: catalyst heater element
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required

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