Reference meaning
What does this code mean?
P0171/P0172 refer to bank 1; P0174/P0175 to bank 2. Lean or rich describes the controller's mixture assessment, not a direct measurement of a failed part. Compare fuel trims at idle and under load, inspect air and exhaust leaks, and test fuel supply or sensor readings using vehicle-specific limits.
Sources and interpretation [1]
A code identifies a detected condition, not a part that must automatically be replaced.
Narrow by vehicle
A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Scan worksheet →Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
P0174Rear/Front Bank Fuel System Too Lean
P0174Fuel System 2/1 Lean
P0174System Too Lean Bank 1/Bank 2
Manufacturer communications
171Original wording in English
JEEP, RAM
Disconnected Purge Line Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): ● P0300-00 - Multiple Cylinder Misfire. ● P0171-00 - System Too Lean Bank 1. ● P0174-00 - Fuel System 2/1 Lean. Customers may also experi…
TOYOTA
Some 2023 – 2024 model year Sequoia Hybrid and 2022 – 2024 model year Tundra and Tundra Hybrid vehicles may exhibit lack of power during acceleration and/or a MIL ON condition with one or more of the following Diagnostic Trouble Codes (DTCs): •P017400 – System Too Lean Bank 2 •P117B00 – Fuel Performance/Direct Injector •P043000 …
JEEP
Flash: Powertrain Control Module (PCM) Updates Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find one or more of the following Diagnostic Trouble Codes (DTCs) have been set: ? P0171 - Fuel System 1/1 Lean. ? P0174 - Fuel System 2/1 Lean. This bulletin invo…
TOYOTA
TSB: Some 2023 model year Sequoia Hybrid and 2022 ? 2023 model year Tundra and Tundra Hybrid vehicles may exhibit poor acceleration and/or a MIL ON condition with one or more of the following Diagnostic Trouble Codes (DTCs): ?P017400 ? System Too Lean Bank 2 ?P117B00 ? Fuel Performance/Direct Injector ?P043000 ? Catalyst System …
Check vehicle applicability
925A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Sources and interpretation
These explanations are editorial summaries of the linked manufacturer material. PDF page numbers count from the first file page. Original publications are in English; translations are reference aids. A cited edition is not a claim that it is the manufacturer's latest instruction.
- 2024–2025 MY OBD System Operation Summary for Gasoline Engines ↗
Ford Motor Company · PDF page(s) 21, 22 · 2024-04-16
Source check date · 2026-10-27
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.