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.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Rough idle, possible stalling
- Hesitation or hard cold start
- Power loss under load
Common causes
Ordered by how often each turns out to be the cause.
- Vacuum leak under loadCommon
- Low fuel pressure / weak pumpPossible
- Contaminated MAF sensorPossible
Parts involved
- Intake Manifold
- Vacuum Hoses
- Mass Air Flow Sensor
- Fuel Pump
- Fuel Injector
P2177 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.