P2187 — System Too Lean at Idle Bank 1

P2187: System Too Lean at Idle Bank 1 — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

System Too Lean at Idle Bank 1. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Powertrain

Symptoms

  • The engine warning lamp may be on, with a rough or unstable idle.
  • An intake hiss, hesitation or occasional stalling may be noticed.

Possible causes

  • A vacuum or PCV leak may admit unmetered air at idle on bank 1.
  • An exhaust leak, misleading MAF/oxygen-sensor data or inadequate fuel delivery may also suggest or cause a lean mixture.

What to check

  • Check related codes and compare fuel-trim values at idle with values at higher engine speed.
  • Inspect vacuum hoses, PCV connections and intake seals for leakage.
  • If no intake leak is found, evaluate upstream exhaust leaks, sensor signals and fuel delivery.

Also written as: P2187-00, P218700 (some scan tools add the fault-type byte, e.g. -00).