P0174 on a Toyota: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

Drivable short-term, but a lean condition on bank 2 should be diagnosed soon to avoid drivability issues.

What P0174 means on a Toyota

On a Toyota, P0174 means the engine is running lean on bank 2 — the side opposite cylinder 1 — because too much air or too little fuel is getting in. Toyota's computer has added as much fuel as it can and still can't balance the mixture. It's the bank 2 version of P0171.

Is P0174 common on Toyotas?

P0174 is most common on Toyota V6 models like the Camry, Highlander, Sienna, and RAV4 V6, since only V6 engines have a bank 2. Cracked intake air hoses between the air filter box and throttle body are a well-known Toyota issue that lets in unmetered air. Vacuum leaks and dirty MAF sensors are also frequent causes on higher-mileage Toyotas.

Commonly reported on: Camry, Highlander, Sienna, RAV4.

Symptoms

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

Common causes

most common: Cracked intake air hose between air box and throttle body
common: Vacuum leak (cracked hose or intake gasket)
common: Dirty or failing mass air flow (MAF) sensor
less common: Faulty upstream oxygen sensor (bank 2)
less common: Weak fuel pump or clogged fuel filter

How to fix it

Fix	DIY?	Typical cost
Inspect and replace the cracked intake air hose	Yes	$20–80
Clean the mass air flow sensor with MAF cleaner spray	Yes	$10–20
Inspect and repair vacuum leaks (hoses, gaskets)	Yes	$10–100
Replace the bank 2 upstream oxygen sensor if it's reading wrong	Yes	$60–200

Frequently asked questions

Why is P0174 common on Toyota V6 engines?

The rubber intake air hose on many Toyota V6s cracks with age, letting extra air in after the MAF sensor. That extra air makes the engine run lean.

What does bank 2 mean on a Toyota?

Bank 2 is the side of the engine that does not contain cylinder 1. Only Toyota models with a V6 or V8 have a bank 2, so 4-cylinder Toyotas won't set P0174.

Can I keep driving my Toyota with P0174?

Short trips are fine, but a lean condition can cause rough idle and hesitation over time. Have it diagnosed soon so a small leak doesn't turn into a bigger repair.