P0171 on a 2021 Hyundai Palisade

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 2021 Hyundai Palisade

Ranked from 413 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Vacuum or intake air leak
Medium severity
A cracked intake boot, brake booster hose, or PCV hose lets unmetered air in and is the single most common cause of a lean bank code; listen for a hiss and check smoke-test results. One owner's report of a shaking, underpowered engine with the CEL on is consistent with an air leak, though it was not confirmed as such.
Reported in 1 NHTSA complaint
2
Weak fuel delivery from failing/clogged injectors
Medium severity
Injectors that are fouled or failing to deliver full volume starve one or more cylinders of fuel, pushing bank fuel trim lean; one complaint describes stalling/rough idle that was diagnosed as needing all 6 injectors replaced.
Reported in 1 NHTSA complaint
Parts:fuel injector set fuel injector seals
3
Dirty or failing MAF sensor
Low severity
A contaminated or drifting mass airflow sensor under-reports intake air, causing the PCM to add less fuel than needed; cleaning or replacing it often resolves the trim fault.
Common cause
4
Weak fuel pump or clogged fuel filter
Medium severity
Reduced fuel pressure across the board produces a lean condition especially under load; check fuel pressure at idle and under acceleration against spec.
Common cause
Parts:fuel pump fuel filter
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open admits excess crankcase air into the intake, leaning out the mixture; inspect/replace the valve and hose.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the front O2/air-fuel sensor
Low severity
A leaking manifold or downpipe joint draws in outside air that the upstream sensor reads as excess oxygen, tricking the PCM into leaning the mixture.
Common cause
7
Intake manifold gasket failure
Medium severity
A failed intake gasket is a classic unmetered-air source on V6/V8 and some inline engines; look for a rough idle that smooths with propane/smoke around the manifold seams.
Common cause
Parts:intake manifold gasket

Part links go to Amazon search results for this vehicle. As an Amazon Associate, WrenchConnect earns from qualifying purchases — always confirm fitment for your exact trim and engine before ordering.

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