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

P2177

System Too Lean Off Idle Bank 1

Fuel trim values on bank 1 indicate a lean condition during off-idle operation. The ECU has to add significant fuel correction to maintain stoichiometric mixture above idle.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number1 / 77

Possible causes

  • Vacuum leak under load high
  • Low fuel pressure / weak pump medium
  • Contaminated MAF sensor medium

Symptoms

  • Check engine light on
  • Rough idle, possible stalling
  • Hesitation or hard cold start
  • Power loss under load

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 80–600 €
  • Estimated time: 0.5–3 h
  • Component: intake manifold
  • Component: vacuum hoses
  • Component: mass air flow sensor
  • Component: fuel pump
  • Component: fuel injector
  • 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