Code Definition

P0174 — System Too Lean (Bank 2)

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Toyota

About P0174

P0174 is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Toyota vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0174 is stored, the module has detected a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0174 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0174 fault code is set when the Engine Control Module (ECM) detects that the air-fuel mixture in Bank 2 of the engine is too lean, meaning there is a higher proportion of air compared to fuel. This condition is typically identified through the oxygen sensors, which sense a higher level of oxygen in the exhaust than normal. A lean mixture can be caused by various factors, including a decrease in fuel delivery or an increase in air intake, as well as potential sensor malfunctions. This lean condition can lead to issues such as engine misfire, rough idle, or lack of power, and it can increas...

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