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
CADILLAC
Reported code forms P0174
CADILLAC: SES LIGHT WITH DTCS P0171 AND P0174. COMPLAINT OF SES LIGHT BUT IT IS UNLIKELY THAT THERE WILL BE A COMPLAINT OF ANY ENGINE PERFORMANCE CONCERNS IF THIS APPLIES. UPON INSPECTION, DTCS P0171 AND P0174 WILL BE…
CADILLAC
Reported code forms P0174
CADILLAC: CHECK ENGINE LIGHT ON, DTC P0174 SET (CHECK FOR VACUUM LEAK AND REPLACE ECM, IF NECESSARY). IF THE UPDATED ECM IS INSTALLED WITHOUT OBTAINING THE 2009 MODEL YEAR CALIBRATIONS, THE VEHICLE MAY RETURN WITH A…
Check vehicle applicability
2A 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.
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.