OBD
P2187
System Too Lean at Idle (Bank 1)
What it means
P2187 means System Too Lean at Idle (Bank 1).
Check these first
- Vacuum leak at idle only
- Faulty or contaminated mass air flow sensor
- Fuel pressure or injector issue at idle
- Failing PCV valve or hose
- Brake booster vacuum leak
What to do next
- Compare fuel trims at idle vs under load
- Smoke-test the intake system for vacuum leaks
- Clean and test the MAF sensor
- Check PCV and brake booster hoses
- Repair the vacuum leak and confirm trims return to normal
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.