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.
Manufacturer communications
2Original wording in English
BUICK, CADILLAC, CHEVROLET, GMC
Reported code forms P0171
This engineering informational bulletin ends the need for information from the field on vehicles that have the condition of Malfunction Indicator Lamp Illuminated with DTC P0171 and/or P0174.
BUICK, CADILLAC, CHEVROLET, GMC
Reported code forms P0171
This engineering informational bulletin is requesting information from the field on vehicles that have the condition of Malfunction Indicator Lamp Illuminated with DTC P0171 and/or P0174.
Check vehicle applicability
1A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Buick | LACROSSE | 2017 |
Historical records · 7 · Historical vehicle association; OBD-II compatibility is not established by this record.
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.
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 ·
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.