P0171 on a 2015 Ram 1500

P0171 means the engine computer is adding more fuel than normal on bank 1 because it sees too much air or not enough fuel.

Not your vehicle? See general P0171 info.

Most common causes on the 2015 Ram 1500

Ranked from 1,427 NHTSA owner complaints filed for this vehicle.

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1
Exhaust Leak (Exhaust Manifold Bolts)
Medium severity
Broken exhaust manifold bolts cause an exhaust leak before the O2 sensor, introducing outside air and causing a false lean reading. Look for broken bolts, soot marks, and a ticking noise on startup.
Reported in 3 NHTSA complaints
2
Vacuum Leak (Intake Manifold / Hoses)
Medium severity
Unmetered air entering the engine after the MAF sensor leans out the air/fuel mixture. Look for cracked hoses, loose clamps, or a leaking intake manifold gasket.
Common cause
3
Faulty Oxygen (O2) Sensor
Low severity
A degraded or failing upstream O2 sensor can falsely report a lean condition, causing the PCM to trigger the code. Confirm with live data showing a stuck or slow-switching sensor voltage.
Common cause
4
Low Fuel Pressure (Failing Fuel Pump or Filter)
High severity
Inadequate fuel delivery prevents the engine from maintaining the proper air/fuel ratio, resulting in a lean condition. Test fuel pressure at the rail to confirm it meets specifications.
Common cause
5
Dirty or Faulty Mass Air Flow (MAF) Sensor
Low severity
A contaminated MAF sensor under-reports the amount of air entering the engine, causing the PCM to inject less fuel. Inspect the sensor wire for dirt or oil and check MAF g/s readings on a scan tool.
Common cause
6
Clogged Fuel Injectors
Medium severity
Restricted injectors fail to spray the commanded amount of fuel, leading to a lean mixture in one or more cylinders. Confirm by performing an injector balance test or checking for specific cylinder misfires.
Common cause

These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0171 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Rough idle
Hesitation
Surging idle
Poor fuel economy

What to check before replacing parts

Review short- and long-term fuel trims on bank 1

Look for: High positive trims (commonly worse at idle, improving with RPM) mean the computer is adding fuel to compensate for excess air or insufficient fuel — that pattern is this code's fingerprint.

Smoke-test the intake

Look for: Smoke escaping (or a hiss you can hear) at intake boots, gaskets, or vacuum hose connections confirms unmetered air is entering after the MAF sensor, which is the most common cause of a lean code.

Inspect the PCV hoses and valve

Look for: A cracked, split, or disconnected PCV hose, or a PCV valve stuck open, draws in extra unmetered air the same way a vacuum leak does.

Clean and test the MAF sensor

Look for: Visible dirt or oil film on the sensor element, or a grams/second reading that doesn't track expected airflow for RPM, means the MAF is under-reporting air and causing the computer to under-fuel.

Verify fuel pressure

Look for: Pressure below spec (weak pump, clogged filter, failing regulator) starves the engine of fuel and produces the same lean trim pattern as a vacuum leak — rule it out before chasing leaks.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Car Runs Rough