P2187 - System Too Lean at Idle (Bank 1)

The Technical Definition: It means the engine computer has detected an overly lean air-fuel mixture, meaning there is too much air and too little fuel. The code sets when the ECM can no longer correct the lean condition by adding fuel because its fuel adjustment has reached its maximum limit. P2187 specifically applies to Bank 1, the cylinder bank that includes cylinder #1.

Common Symptoms: Because this code specifically triggers at idle, you will likely notice the car stumbling at stoplights, though performance may feel normal at highway speeds.

Typical Fix: Common DIY fixes include cleaning the MAF sensor, replacing cracked vacuum hoses, swapping a faulty PCV valve, or changing a stuck EVAP purge valve.