P2177System Too Lean Off Idle (Bank 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2177 means bank 1's long-term trim has to add too much fuel once the engine is off idle, at part load and while accelerating. Bosch-type systems learn this as a multiplicative factor that scales with airflow, unlike the additive idle part behind P2187. GM's 2005 V6 and 2008 3.6 LLT set it above a factor of 1.23, GM's 2023 and 2024 tables above 1.27, both over two trips. Saab's 9-5 2.0T of 2010 checks at 6.9 to 41.7 g/s, 18 to 80 % load and 1280 to 4000 rpm and needs 4 s in a row or 50 s in total. VW's 2014 CC 2.0 TSI allows up to +28 %. Lean at load points to a weak fuel supply, an air mass sensor reading low or leaks under boost. Bulletins: Mazda CX-7 A/F sensor wiring, Audi RS 3 and TT RS software, Mercedes M254 fuel boiling.
- What you may notice
- Check engine lamp on after two trips
- Hesitation or lack of power when accelerating
- Likely causes
- LikelyFuel pressure too low under load, for example a weak pump or clogged filter
- PossibleAir mass sensor reading too low or contaminated
- PossibleLeak after the air mass sensor, often on the boost side
- RareCalibration error or damaged A/F sensor wiring covered by bulletins
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.