P0171 on Lexus: How to Diagnose & Fix
System Too Lean (Bank 1)
1 Lexus model · 1 documented issue · 1 critical
P0171 on Lexus by model: symptoms, diagnosis and fix
The low-pressure fuel pump inside the fuel tank can fail, cutting fuel supply and stalling the engine — potentially at speed and in traffic. This is the same Denso low-density impeller family of failures that ran across a very large number of Toyota and Lexus products, in which the impeller absorbs fuel, swells, and binds in the pump housing. NHTSA campaign 25V028000 covers 2019 Lexus NX300 alongside the 2018 Camry and 2019 RX350L. Owner notification letters were mailed March 12, 2025, and the campaign numbers are 25LA01 for Lexus and 25TA01 for Toyota. The remedy is replacement of the fuel pump assembly.
Common Symptoms
- Engine stalls while driving
- Long crank or no restart when hot
- Hesitation, sputtering, or power loss under load
- Whining or buzzing from the fuel tank
- Check engine light with fuel system codes
How to Fix
Have the dealer replace the fuel pump assembly under recall 25LA01 / NHTSA 25V028000, free of charge, and confirm by VIN that it was actually performed on a used purchase. The failure gives warning before it strands you: a binding impeller drags first, so long hot cranking, hesitation or sputtering under load, rough running at highway speed, and a whine from the tank are the precursors. Do not pay a shop to replace an in-tank pump on an affected VIN — this is covered. If the vehicle has already stalled, say so, since the dealer will want to check for consequential damage.
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Sources for this issue (1)
P0171 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0171 mean on a Lexus?
P0171 stands for "System Too Lean (Bank 1)." This code means the engine's computer has detected that the air-fuel mixture on Bank 1 (the side of the engine with cylinder #1) is running too lean — meaning there is too much air relative to fuel. The computer watches the oxygen sensors and has had to add a large amount of extra fuel (long-term fuel trim) to try to compensate, but it has hit its correction limit. A lean condition can cause rough idle, hesitation, reduced power, and over time can run the engine hotter than normal. It usually points to either unmetered air leaking into the engine or not enough fuel being delivered. On Lexus it is documented across 1 model: NX.
What are the most common causes of P0171?
The most common causes of P0171 are: Vacuum or intake air leak (cracked hose, gasket, or PCV system), Dirty or failing mass airflow (MAF) sensor, Weak fuel pump or restricted fuel filter, Clogged or dirty fuel injectors, Faulty or aged upstream oxygen sensor, Leaking intake manifold gasket, Low fuel pressure or failing fuel pressure regulator, Exhaust leak ahead of the oxygen sensor. The specific cause varies by vehicle.
How much does it cost to fix P0171 on a Lexus?
Repair costs vary widely with the root cause and Lexus model; each issue on this page carries its own estimate where one is published.
Looking for P0171 on a different make?
View P0171 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.