P0171 on a Jeep: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

Drivable for a short time, but a lean condition can cause rough idling and misfires, so get it checked soon.

What P0171 means on a Jeep

On a Jeep, P0171 means bank 1 is running lean, so the engine is getting too much air or not enough fuel. The Jeep engine computer has already added as much fuel as it can and still sees a lean mixture, so it turns on the check engine light.

Is P0171 common on Jeeps?

P0171 is common on older Jeeps, especially the 4.0L inline-six in the Cherokee and Wrangler, where aged vacuum lines leak air. The 3.6L Pentastar V6 can also set it with a dirty MAF or a leaking PCV hose. On Wranglers, water or mud exposure can contaminate the MAF sensor.

Commonly reported on: Wrangler, Cherokee, Grand Cherokee, Liberty.

Symptoms

Check engine light on
Rough or surging idle
Hesitation or lack of power
Poor fuel economy

Common causes

most common: Cracked or disconnected vacuum lines, common on the 4.0L inline-six
common: Dirty or failing mass air flow (MAF) sensor
common: Leaking throttle body or intake gasket
less common: Clogged PCV valve or hose
less common: Weak fuel pump or clogged fuel filter

How to fix it

Fix	DIY?	Typical cost
Replace cracked vacuum hoses and recheck connections	Yes	$10–60
Clean the MAF sensor with MAF cleaner spray	Yes	$10–20
Replace a leaking throttle body or intake gasket	Yes	$20–80
Have fuel pressure tested and replace a weak pump if needed	Mechanic	$300–700