Code Definition

P2178 — Fuel Trim Rich During Cruise/Acceleration (Bank 1)

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

About P2178

P2178 is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Holden vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P2178 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 P2178 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 Engine Control Module (ECM) continuously monitors short term and long term fuel trim using feedback from the oxygen sensors during closed loop operation. DTC P2178 is set when, during steady cruise or acceleration, the ECM must apply excessive negative fuel trim on bank 1 to hold the commanded air fuel ratio, meaning it is pulling fuel out to compensate. This indicates the base mixture on bank 1 is richer than expected and exceeds the calibrated correction limit for a set time. A persistent rich condition can foul spark plugs, raise emissions and fuel consumption, and may produce a fuel sm...

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