P0171 on Mitsubishi
System Too Lean (Bank 1)
P0171 on Mitsubishi vehicles indicates system too lean (bank 1). Au7o has documented this code across 1 Mitsubishi model — most commonly on Eclipse. 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. Typical repair costs on Mitsubishi range from $75 to $400, depending on the specific model and root cause.
Common Causes of P0171
- •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
P0171 on Mitsubishi by Model
Mitsubishi Eclipse(1 issue)
- 2G Fuel Pump Wiring Voltage Drop and Fuel Pump/MFI Relay Failure1995-1999
On 1995-1999 cars the fuel pump's factory wiring is undersized and its chassis ground (at the floor crossmember under the driver's seat) corrodes with age, dropping voltage at the pump into the 10-11V range under load. The paired fuel pump/MFI relay behind the center console can also fail. The result is intermittent cranking no-starts (no pump prime), stalling, and lean stumble or fuel cut at wide-open throttle on turbo cars — a problem so common the community-standard fix is the documented 'fuel pump rewire.'
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View P0171 across all makes →Frequently Asked Questions
What does P0171 mean on Mitsubishi?▼
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 Mitsubishi specifically, this code is documented across 1 model.
What causes P0171 on Mitsubishi vehicles?▼
Common causes on Mitsubishi: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0171 on a Mitsubishi?▼
Repair costs on Mitsubishi range from $75 to $400, depending on the specific model and root cause.
Which Mitsubishi models have P0171 documented?▼
Au7o has documented P0171 on 1 Mitsubishi model: Eclipse.