OBD-II code · Powertrain (generic, extended)
P2187 System Too Lean at Idle (Bank 1)
Fuel trim on bank 1 hits the lean limit only at idle, while trim returns to normal at higher load. This pattern strongly indicates a vacuum leak — leaks become a larger fraction of total airflow at idle and so dominate the trim, but disappear into background noise above idle.
Is it safe to drive with P2187?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyVacuum leak (intake gasket, brake booster, hoses)
- PossiblePCV valve stuck open
Symptoms
- Check engine light on
- Rough idle, possible stalling
- Hesitation or hard cold start
- Power loss under load
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–4 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Intake Manifold, Pcv Valve, Brake Booster, Vacuum Hose
Related codes
- P0171System Too Lean (Bank 1)
- P2189System Too Lean at Idle (Bank 2)
- P2184Engine Coolant Temperature Sensor 2 Circuit Low
- P2185Engine Coolant Temperature Sensor 2 Circuit High
- P2186Engine Coolant Temperature Sensor 2 Circuit Low
- P2188System Too Rich at Idle (Bank 1)
- P218AThrottle Actuator B Control System - Idle Position Not Learned
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.