Code Definition

P0173 — Fuel Trim Malfunction (Bank 2)

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

About P0173

P0173 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0173 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 P0173 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 P0173 fault code is set when the Engine Control Module (ECM) detects an issue with the fuel trim on Bank 2 of the engine. Fuel trim refers to the adjustments the ECM makes to the fuel mixture in response to various data inputs, aiming to maintain the ideal air-fuel ratio for efficient combustion. This code indicates that the ECM is compensating for either a rich or lean condition beyond normal operational parameters. Common causes for this malfunction can range from fuel delivery issues to air intake problems or sensor faults. The code suggests that the ECM is continuously trying to correc...

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