OBD codes / P0171 / Toyota Tacoma
P0171 on a Toyota Tacoma
System Too Lean (Bank 1)
2.7L 2TR-FE four, 4.0L 1GR-FE V6, and 3.5L 2GR-FKS V6 (bank 1).
What P0171 usually means on a Tacoma
P0171 means the Tacoma is running lean on bank 1 — the ECU is adding fuel to make up for extra air or a fuel shortfall. On these engines the typical culprits are a contaminated mass-airflow sensor or a vacuum leak from a cracked PCV hose or tired intake gasket. Higher-mileage trucks can also drift lean from a weak fuel pump or tired injectors. It may idle roughly, hesitate, or surge, and a severe lean condition can misfire.
Most likely causes on this model
- Dirty MAF sensor
The Tacoma's hot-wire MAF gets contaminated and under-reports airflow; cleaning often clears it.
- Vacuum leak
Cracked PCV hoses or a hardened intake gasket admit unmetered air on older Tacomas.
- Weak fuel delivery
A tired pump or dirty injectors push trims lean under load on high-mileage trucks.
- Failing air-fuel sensor
The Denso air-fuel sensor gets sluggish with age and reports the mixture inaccurately.
What it costs on a Tacoma
Cleaning the MAF or replacing a vacuum hose is cheap and resolves most Tacoma P0171 cases, and those parts are easy to reach. A fuel pump or AF sensor is a larger spend but less common. Read live fuel trims before buying parts so you fix the actual cause.
Year, engine and mileage change the answer. Get a diagnosis for your Tacoma — it weighs these causes against your exact configuration and real complaint data.
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Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0171 behavior is covered on the main P0171 page. Confirm with a scan tool before buying parts.