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

P2AA2

Alternative Fuel Return Line Insufficient Flow

The AFCM detects that the flow through the alternative fuel return line is below the expected minimum for the active operating mode. Restricted line, stuck valve, or pump output too low.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / numberA / A2

Possible causes

  • Return line restricted by debris high
  • Return line valve stuck closed medium

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 150–700 €
  • Estimated time: 1–4 h
  • Component: alt fuel return line
  • Component: alt fuel return line valve
  • Component: alt fuel pump
  • MIL / check engine light
  • emissions-relevant
  • limp mode possible

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