P0171 on a 2019 Ram 1500 Classic

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 2019 Ram 1500 Classic

Ranked from 1,453 NHTSA owner complaints filed for this vehicle.

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1
Exhaust leak upstream of the O2 sensor from a cracked exhaust manifold
Medium severity
The 5.7L Hemi's known cracked-exhaust-manifold issue is described repeatedly on this vehicle; a leak ahead of the upstream O2 sensor draws in outside air and skews the sensor toward a false-lean reading.
Reported in 3 NHTSA complaints
Parts:exhaust manifold exhaust manifold gasket
2
Weak or failing fuel pump
High severity
Two owners report a failed/failing fuel pump (one under a fuel-pump recall) causing no-start and recurring stalling with a fuel-related trouble code — insufficient pump output leans the mixture under load.
Reported in 2 NHTSA complaints
Parts:fuel pump
3
Vacuum or intake leaks
Medium severity
Cracked hoses, a bad brake-booster line, or an unseated intake boot admit unmetered air, driving bank 1 lean.
Common cause
4
Dirty or failing MAF sensor
Low severity
An underreporting MAF causes the PCM to under-fuel; check for a contaminated sensor element or wiring/connector fault.
Common cause
Parts:mass air flow sensor
5
Clogged fuel filter restricting delivery
Medium severity
Restricted fuel flow drops rail pressure under demand, producing the same lean symptom as a weak pump.
Common cause
Parts:fuel filter
6
Stuck-open PCV valve
Low severity
A PCV valve stuck open admits excess, unmetered crankcase air into the intake, leaning the mixture particularly at idle.
Common cause
Parts:PCV valve

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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