P0171 on a 2016 Hyundai Tucson Fuel Cell

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 2016 Hyundai Tucson Fuel Cell

Ranked from 1,536 NHTSA owner complaints filed for this vehicle.

Sort by:

1
MAF sensor fouled by oil consumption (Theta II engine defect)
Medium severity
This engine is subject to a well-documented Hyundai Theta II GDI oil-consumption/rod-bearing defect; several owners report oil burning together with sluggish acceleration, misfire, or stalling, consistent with oil residue fouling the MAF sensor and skewing airflow readings lean.
Reported in 5 NHTSA complaints
Parts:mass airflow sensor
2
Weak fuel pump or stuck-open EVAP purge valve
Medium severity
Owner had the fuel pump and purge solenoid replaced after an intermittent no-accelerate/RPM-flare condition, suggesting either inadequate fuel delivery or unmetered air being pulled through the purge circuit.
Reported in 1 NHTSA complaint
Parts:fuel pump purge valve
3
Dirty or failing fuel injector(s)
Medium severity
Owner reported the check engine light returning after a fuel-injector-related failure that also affected starting/driveability.
Reported in 1 NHTSA complaint
Parts:fuel injector
4
Vacuum or intake leak
Medium severity
Check intake boots, PCV hose, and brake booster line for cracks; a leak downstream of the MAF lets unmetered air in, causing a lean reading at idle.
Common cause
5
PCV valve stuck open
Low severity
A PCV valve stuck open pulls excess unmetered air into the intake, especially noticeable at idle and light load.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the front O2/A-F sensor
Low severity
A leak ahead of the air-fuel sensor draws in outside air and skews the sensor toward a false lean reading.
Common cause
7
Intake manifold gasket leak
Medium severity
A worn intake manifold gasket admits unmetered air, most noticeable at idle and often accompanied by a rough/erratic idle.
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