What are the symptoms of P0171?

Common symptoms include: Hesitation or surging; Reduced power; Rough idle.

What causes a P0171 code?

The most common causes are: Intake/boost leak (unmetered air); Weak fuel supply; Dirty MAF; Vacuum leak.

How do you fix P0171?

Smoke/boost-test the intake for leaks; Check fuel supply pressure and filters; Clean or test the MAF. Worth diagnosing soon — left alone, the underlying issue can grow into a bigger, costlier problem.

OBD-II Code Lookup

P0171Watch

System Too Lean (Bank 1)

Fuel/Air system

The mixture is running leaner than the computer wants on bank 1 — more air or less fuel than expected. On diesels this often surfaces as an air/fuel metering discrepancy.

Worth diagnosing soon — left alone, the underlying issue can grow into a bigger, costlier problem.

Common symptoms

Hesitation or surging
Reduced power
Rough idle

Common causes

Intake/boost leak (unmetered air)
Weak fuel supply
Dirty MAF
Vacuum leak

How it's diagnosed & fixed

Smoke/boost-test the intake for leaks
Check fuel supply pressure and filters
Clean or test the MAF

Got P0171? Get it diagnosed.

A real technician can interpret P0171 in the context of your truck and symptoms — and tell you what's actually wrong before you buy parts.

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Related guides

Turbo Trouble: Overboost vs. Underboost

Reference only. A trouble code names a symptom, not the failed part — always confirm with a live diagnosis before repairs. See our Knowledge Base for deeper guides.