P0171 on a 2019 Jeep Wrangler

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 Jeep Wrangler

Ranked from 721 NHTSA owner complaints filed for this vehicle.

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1
Vacuum Leak / Unmetered Air
Medium severity
Unmetered air entering the intake manifold causes a lean condition. Several complaints note uncommanded high engine revving and high idle, which are classic symptoms of a severe vacuum leak or intake manifold issue.
Reported in 4 NHTSA complaints
2
Coolant Intrusion / Sensor Fouling
High severity
Coolant leaking into the combustion chamber or exhaust can foul O2 sensors and disrupt combustion, potentially triggering lean or misfire codes. Complaints specifically note 2.0L coolant leaks and head gasket failures.
Reported in 3 NHTSA complaints
3
Faulty Upstream Oxygen (O2) Sensor
Low severity
A degraded or faulty O2 sensor can falsely report a lean condition to the PCM. Confirm by monitoring live O2 sensor voltage data to see if it is stuck lean.
Common cause
4
Low Fuel Pressure (Fuel Pump/Filter)
Medium severity
If the fuel pump is failing or the filter is clogged, the engine will not receive enough fuel, causing a genuine lean condition. Verify with a mechanical fuel pressure gauge.
Common cause
5
Dirty or Clogged Fuel Injectors
Medium severity
Restricted fuel injectors will not spray the commanded amount of fuel, leading to a lean mixture in the affected bank. Look for accompanying misfire codes and perform an injector balance test.
Common cause
6
Faulty MAP or MAF Sensor
Low severity
An inaccurate Manifold Absolute Pressure or Mass Air Flow sensor will cause the PCM to miscalculate the required fuel. Check for dirty sensor elements or skewed data readings on a scan tool.
Common cause
7
Exhaust Leak (Pre-O2 Sensor)
Medium severity
An exhaust leak before the upstream O2 sensor draws in outside air via the Venturi effect, tricking the sensor into reading a lean condition. Listen for ticking noises near the exhaust manifold.
Common cause
8
PCV System Failure
Low severity
A stuck open PCV valve or cracked PCV hose acts as a vacuum leak, introducing excess air into the intake. Inspect the PCV valve and hoses for proper operation and physical damage.
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