CASE 01Fuel controlIntermediate9 minutes

Lean at warm idle

2018 turbocharged gasoline sedan · MIL on; occasional rough warm idle

Simulated evidenceNo vehicle commandsEvery decision explained

THE FAILURE SCENE

The vehicle is fully warm and stationary. The scan is complete, the fuel-control state is closed loop, and no severe shaking or flashing MIL is present.

DTCP0171 stored

Bank 1 correction crossed the controller's lean threshold.

Freeze frame742 rpm · 9% load · 196°F

The fault matured at warm idle, not under road load.

Fuel correction+24% idle · +7% at 2,500 rpm

The correction is strongest at idle and improves with airflow.

Supply14.1 V running

The captured controller supply does not show low voltage.

DECISION 1 / 3

What is the strongest first conclusion?

The pattern is repeatable across two warm-idle captures.