P0171 — System Too Lean (Bank 1)

Q: What does fault code P0171 mean?

P0171 means: System Too Lean (Bank 1). It is a Powertrain (engine/transmission) fault code defined by the OBD-II standard.

Q: Can I keep driving with P0171?

With P0171 you can usually drive home and book an inspection within a few days unless the car feels abnormal.

Powertrain (engine/transmission)

P0171 signifies that the fuel trim system is operating too lean on Bank 1. This means the engine control module (ECM) is detecting too much air or not enough fuel in the exhaust gases for the specified engine load.

The powertrain control module (PCM)/ECM monitors the air-fuel mixture feedback from the oxygen sensors to ensure the engine operates within optimal parameters for fuel efficiency and emissions control.

Läs på svenska

Can I drive with P0171?

You can usually drive home and book an inspection within a few days.

Likely root causes

Vacuum leak in the intake system (e.g., vacuum hoses, intake manifold gasket)
Faulty Mass Airflow (MAF) sensor (reporting inaccurate air intake to the ECM)
Clogged or failing fuel injector(s) on Bank 1 or a weak fuel pump/pressure regulator

Common symptoms with P0171

Engine runs rough
Engine stalls
Hard to start

Full symptom matching, likelihood scoring and related codes for your specific vehicle require a diagnosis.

Frequently asked questions

What does fault code P0171 mean?

P0171 means System Too Lean (Bank 1).

Can I keep driving with P0171?

You can usually drive home and book an inspection within a few days.

What symptoms are common with P0171?

Engine runs rough, Engine stalls, Hard to start

Related fault codes

Get a full diagnosis for P0171 with AutoUncover.