What does code P0171 mean on a Toyota and is it safe to drive?
P0171: System Too Lean (Bank 1). Here's what it means on your Toyota, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
What this code means
The engine is getting too much air relative to fuel. The O2 sensor sees excess oxygen in the exhaust and the PCM is adding more fuel than normal to compensate.
Common causes for your Toyota
- Dirty or faulty mass airflow (MAF) sensor
- Vacuum leaks (PCV hose, intake gasket, brake booster)
- Weak fuel pump or clogged fuel filter
- Leaking or stuck open fuel injectors (less common)
Symptoms
- Check Engine Light
- Rough idle, hesitation, lack of power
- Possible spark knock under load
- Poor fuel economy
Typical fixes
- Clean or replace MAF sensor
- Locate and seal vacuum leaks
- Replace fuel filter / test fuel pressure
- Smoke test intake system
Repair cost range
For a Toyota, repairs for P0171 often fall between $50 and $500, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Toyota
Toyota P0171 on the 2.5L 2AR-FE (Camry, RAV4, Venza) is most often caused by a cracked vacuum hose at the brake booster check valve—the hose deteriorates with age and causes a large, obvious leak. Inspect this hose before anything else. On Tacoma 4.0L 1GR-FE, the VVT oil control valve screen clogs with sludge, causing low oil pressure to the cam phaser which alters timing and creates lean-seeming conditions. On 3.5L 2GR-FE V6 engines, intake manifold gasket leaks at the rear runners (hard to see) are common on high-mileage examples.
Most commonly affected models