Fuel Control System B Too Lean Off Idle (Bank 1)
The secondary fuel control loop B on bank 1 reports a lean condition outside idle. On dual-injection systems (port + direct) the secondary loop trims port injection independently from the main loop.
Affected components
- Fuel injector
- Fuel pressure regulator
- Oxygen sensor
Common causes
- High likelihood: Vacuum leak
- Medium likelihood: Port injectors clogged
- Medium likelihood: Fuel pressure low
Possible symptoms
- Check engine light on
- Rough idle, possible stalling
- Hesitation or hard cold start
- Power loss under load
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Related codes
Sources
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.