P2178 — System Too Rich Off Idle Bank 1
Bank 1 fuel trim shows a strong rich correction during off-idle operation. The ECU is forced to subtract fuel to keep the mixture near stoichiometric.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Fuel pressure regulator
- Fuel injector
- Mass air flow sensor
- Evap purge valve
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Leaking fuel injector
- Excessive fuel pressure
- Stuck-open purge valve
Possible symptoms
- Check engine light on
- Increased fuel consumption
- Black smoke from exhaust on acceleration
- Smell of unburned fuel, fouled spark plugs
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.