P0171 on a 2018 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 2018 Jeep Wrangler

Ranked from 1,793 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Intake camshaft / rocker arm wear causing air-fuel ratio imbalance
Medium severity
Owners had an air/fuel ratio imbalance code (P219A) and repeat propulsion loss traced to valvetrain wear/camshaft work on this Pentastar engine, a mechanism closely related to a system-lean condition.
Reported in 2 NHTSA complaints
Parts:camshaft rocker arm
2
Fuel pump relay failure inside the TIPM (Totally Integrated Power Module)
High severity
A documented, widespread JK/JL issue where the fuel pump relay embedded in the TIPM fails, causing intermittent loss of fuel delivery and starting problems that can present as a lean condition.
Reported in 1 NHTSA complaint
Parts:TIPM fuel pump relay
3
Vacuum or intake air leak
Medium severity
The most common general cause of a lean fuel trim code; inspect intake boots, PCV hoses, and brake booster line for cracks.
Common cause
4
MAF sensor contamination or failure
Medium severity
A dirty or failing MAF under-reports intake air, causing the ECU to under-fuel; verify with live data against expected values.
Common cause
5
PCV valve stuck open
Low severity
Introduces excess unmetered air into the intake, most noticeable at idle.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the front oxygen sensor
Low severity
Outside air drawn in ahead of the upstream O2 sensor makes the ECU falsely read lean.
Common cause
7
Intake manifold gasket leak
Low severity
A failed manifold gasket admits unmetered air, often paired with a rough 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