P0171 on a Toyota: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

You can usually drive a Toyota short-term with P0171, but a lean mixture can cause misfires and should be fixed soon.

What P0171 means on a Toyota

On a Toyota, P0171 means bank 1 is running lean — too much air or not enough fuel — and the engine computer can't add enough fuel to fix it. Toyota's ECM compares the MAF sensor reading with the oxygen sensors, and when the mix stays lean past its adjustment limit, it sets P0171.

Is P0171 common on Toyotas?

P0171 is one of the most common codes on Camrys, Corollas, and RAV4s with higher mileage. Cracked or loose intake hoses, a dirty MAF sensor, and a worn PCV valve are the usual Toyota culprits.

Commonly reported on: Camry, Corolla, RAV4, 4Runner.

Symptoms

Check engine light on
Rough or surging idle
Hesitation under acceleration
Worse fuel economy

Common causes

most common: Vacuum leak from a cracked or loose intake hose
common: Dirty or failing mass air flow (MAF) sensor
common: Worn PCV valve or hose
less common: Weak fuel pump or clogged fuel filter

How to fix it

Fix	DIY?	Typical cost
Inspect and replace cracked intake hoses and clamps	Yes	$10–100
Clean the MAF sensor with MAF cleaner	Yes	$10–20
Replace the PCV valve and hose	Yes	$15–60
Replace a weak fuel pump or clogged fuel filter	Mechanic	$300–700