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 wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
P0174System Too Lean Bank 1/Bank 2Manufacturer communications
6Original wording in English
TOYOTA
Reported code forms P0174
TSB: Some 2014 ? 2020 model year Toyota vehicles may exhibit a hard start and/or MIL ON condition with one or more of the following Diagnostic Trouble Codes (DTCs): ?DTC P0171 and/or P0174 (System Too Lean Bank 1/Bank…
TOYOTA
Reported code forms P0174
MALFUNCTION INDICATOR LAMP ON DIAGNOSTIC TROUBLE CODE P0171, P0174, P2195, OR P2197. *AK
TOYOTA
Reported code forms P0174
TDN MAIL MESSAGE REGARDING REPORTS THAT SOME 4-CYLINDER VEHICLES MAY ILLUMINATE THE CHECK ENGINE LIGHT AND SET DIAGNOSTIC TROUBLE CODES (DTC) P1130, P1135, P1150, P1155, P0171 AND / OR P0174 WHEN OPERATED BELOW 30…
TOYOTA
Reported code forms P0174
SUBJECT REGARDING ELECTRONIC CONTROL UNIT (ECU) REPROGRAMMING SUPPORT. CERTAIN 2001 FOUR CYLINDER VEHICLES, IF DRIVEN AT TEMPERATURES BELOW 30 DEGREES F, MAY DISPLAY A MALFUNCTION INDICATOR LAMP (MIL) AND STORE ONE OR…
TOYOTA
Reported code forms P0174
SOME VEHICLES MAY ILLUMINATE THE CHECK ENGINE LIGHT AND SET DIAGNOSTIC TROUBLE CODES P1130, P1135, P1150, P1155, P1071 AND / OR P0174. *JB
TOYOTA
Reported code forms P0174
SOME 4-CYLINDER VEHICLES MAY ILLUMINATE THE CHECK ENGINE LIGHT AND SET DIAGNOSTIC TROUBLE CODES P1130, P1135, P1150, P1155, P0171 AND / OR P0174 WHEN OPERATED BELOW 30 DEGREES F. *TT
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 |
|---|---|---|
| Toyota | HIGHLANDER | 2019 |
| Toyota | HIGHLANDER | 2018 |
| Toyota | HIGHLANDER | 2017 |
| Toyota | HIGHLANDER | 2006 |
| Toyota | HIGHLANDER | 2005 |
| Toyota | HIGHLANDER | 2001 |
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.