OBD-II code · Powertrain (generic, extended)
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.
Is it safe to drive with P2178?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyLeaking fuel injector
- PossibleExcessive fuel pressure
- PossibleStuck-open purge valve
Symptoms
- Check engine light on
- Increased fuel consumption
- Black smoke from exhaust on acceleration
- Smell of unburned fuel, fouled spark plugs
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–3 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Fuel Pressure Regulator, Fuel Injector, Mass Air Flow Sensor, Evap Purge Valve
Related codes
- P2180System Too Rich Off Idle Bank 2
- P2175Throttle Actuator Control System - Low Air Flow Detected
- P2176Throttle Actuator A Control System - Idle Position Not Learned
- P2177System Too Lean Off Idle Bank 1
- P2179System Too Lean Off Idle Bank 2
- P217AFuel Injector Group G Supply Voltage Circuit/Open
- P217BFuel Injector Group G Supply Voltage Circuit Low
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.