P2187: System Too Lean at Idle (Bank 1)

What does P2187 mean?

Bank 1 requires excessive fuel correction specifically at idle. Unmetered air can have a much larger effect at low airflow than during driving, making vacuum, PCV, or purge leaks important diagnostic leads.

Generic OBD-II definition: System Too Lean at Idle (Bank 1). Confirm applicability in your vehicle service information.

Common causes

• Vacuum or PCV-system leak
• Purge valve leaking air at idle
• Incorrect airflow or oxygen feedback
• Low fuel pressure

Symptoms

• Rough or irregular idle
• Hot-start difficulty
• Whistling or hesitation

Diagnostic focus

Trims that improve as RPM rises often suggest an air leak rather than a fuel-supply shortage. Use that pattern as a clue, not proof, and confirm with a controlled leak test.

Can I keep driving with P2187?

Severity: Medium Drive gently and get it diagnosed soon.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Compare fuel trims at idle and higher RPM
• Inspect PCV and purge plumbing and smoke-test for leaks
• Check fuel delivery if trims remain lean beyond idle

Sources & review

• OBD-Codes.com: P2187
• TroubleCodes.net: P2 code definitions

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.