P2187System Too Lean at Idle (Bank 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2187 means the long-term fuel trim of bank 1 has to add more fuel than allowed in the idle and low-load range. Many systems, especially Bosch ones, split mixture adaptation into an additive part, which dominates at low airflow, and a multiplicative part for load. An air leak adds a fixed amount of unmeasured air, which matters most at idle, so it shows up in the additive part. GM's 3.6 V6 engines set the code above 7 % (2005) or 6.1 % (2008 LLT, at 520 to 1120 rpm, 1.7 to 7.8 g/s and coolant above 60 °C), and GM's 2024 tables above about 5.5 %, over two trips. On the Opel/GM 2.0 turbo in the Saab 9-5 (2010) the weighted long-term trim must exceed its limit for 4 s continuously or 50 s in total (Type B). Audi traced P2187 with P2279 on 2.0 TFSI engines to a crankcase ventilation valve that let boost into the crankcase; Mazda found A/F sensor wiring on the CX-7 2.3 turbo shorted after brake fluid was spilled on it.
- What you may notice
- Malfunction indicator lamp on
- Rough or hunting idle, hissing from the engine bay
- Likely causes
- LikelyAir leak after the air mass sensor, often at the crankcase ventilation
- RareDamaged front oxygen or A/F sensor wiring
- RareFuel pressure too low
- 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: €10 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.