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
7Original wording in English
FORD, MERCURY
Reported code forms P0171
MALFUNCTION INDICATOR LAMP ON AND DIAGNOSTIC TROUBLE CODES P0171/P0174 OR P1072/P0175 STORED IN MEMORY OR AS HARD FAULTS. HESITATION, LACK OF POWER OR RUNS ROUGH CONDITION. *TT
FORD, LINCOLN, MERCURY
Reported code forms P0171
SOME VEHICLES MAY EXHIBIT VACUUM OR AIR LEAKS IN THE INTAKE MANIFOLD AND / OR ENGINE SYSTEM CAUSING DIAGNOSTIC TROUBLE CODES P0171 AND OR P0174. *TT
FORD, MERCURY
Reported code forms P0171
SOME VEHICLES MAYE XHIBIT EXHIBIT A MALFUNCTION INDICATOR LAMP ILLUMINATED WITH DIAGNOSTIC TROUBLE CODE P0171 AND P0172 STORED IN MEMORY. *TT
FORD, MERCURY
Reported code forms P0171
BRIEF INFORMATION REGARDING VEHICLES WITH MALFUNCTION INDICATOR LIGHT ON WITH DIAGNOSTIC TROUBLE CODE P0171 SET. *TT
FORD, MERCURY
Reported code forms P0171
VEHICELS BUILT IN JANUARY 1997 MAY EXHIBIT MIL ILLUMINATION WITH A CODE P0171. *TW
FORD, MERCURY
Reported code forms P0171
VEHICLES MAY EXHIBIT MIL ILLUMINATION WITH A CODE OF P0171 - THIS MAY BE CAUSED BY A DISCONNECTED FUEL PRESSURE REGULATOR VCUUM HOSE. *TW
Check vehicle applicability
6A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Ford | CONTOUR | 2000 |
| Ford | CONTOUR | 1999 |
| Ford | CONTOUR | 1998 |
| Ford | CONTOUR | 1997 |
| Ford | CONTOUR | 1996 |
| Ford | CONTOUR | Year not specified |
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.