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

P042E

EGR A Control Stuck Open

EGR valve A is mechanically stuck open — exhaust gas continues to flow into the intake at all times, causing rough idle and lean condition during acceleration.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number4 / 2E

Possible causes

  • Carbon buildup holds valve open high
  • Carbon or debris buildup preventing free movement low
  • Component wear with age - mechanical play low

Symptoms

  • Check engine light on
  • Pinging or knocking under load
  • Power loss and hesitation
  • Possible rough idle
  • Failed emissions inspection (NOx)

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 80–800 €
  • Estimated time: 0.7–3 h
  • Component: egr valve
  • 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