P0171 on a 2018 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 2018 Ram 1500

Ranked from 644 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Weak/failing high-pressure fuel pump (HPFP) reducing fuel delivery
High severity
The EcoDiesel 3.0L HPFP recall (Z46) is tied to fuel starvation and metal debris contaminating the fuel system, which can produce low fuel pressure and a lean condition; several owners report HPFP failure or the Z46 recall directly.
Reported in 4 NHTSA complaints
Parts:fuel pump fuel filter
2
Exhaust manifold leak/broken bolts upstream of the O2 sensor
Medium severity
Broken exhaust manifold bolts (a well-documented Ram issue) let outside air reach the upstream O2 sensor, skewing the reading lean even though the engine is running correctly.
Reported in 2 NHTSA complaints
Parts:exhaust manifold gasket manifold bolts
3
Turbo/intake boost leak (vacuum leak)
Medium severity
A defective turbo component was reported with concern for fuel starvation; a leaking boost/intake connection lets unmetered air into the engine and drives fuel trims lean.
Reported in 1 NHTSA complaint
4
Vacuum or intake hose leaks
Medium severity
Cracked PCV, brake-booster, or intake hoses let unmetered air past the MAF, a classic cause of a lean bank-1 code.
Common cause
5
Dirty or failing MAF sensor
Low severity
A contaminated or drifting MAF under-reports incoming air, causing the PCM to under-fuel and trip a lean code.
Common cause
Parts:MAF sensor
6
Stuck-open PCV valve
Low severity
A PCV valve stuck open adds an unmetered air path into the intake, particularly noticeable at idle.
Common cause
Parts:PCV valve
7
Intake manifold gasket leak
Medium severity
A leaking intake manifold gasket admits unmetered air directly downstream of the throttle body, producing a persistent lean trim.
Common cause
Parts:intake manifold gasket

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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