What it means
Fuel control system B on bank 1 has detected a lean condition off idle. The code identifies the operating condition and fuel control system; it does not specify a particular injection type or cause.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Fuel control system B adjusts fueling for bank 1 using feedback from the engine's air-fuel and oxygen sensing system. This code sets when the system detects a lean mixture in bank 1 while the engine is off idle, suggesting that air, fuel delivery, or feedback is out of balance in that operating range.
Common causes
Most likely first.
- Vacuum leak
- Port injectors clogged
- Fuel pressure low
Symptoms
- Check engine light on
- Rough idle, possible stalling
- Hesitation or hard cold start
- Power loss under load
How to diagnose it
- Save freeze-frame data and review bank 1 fuel trims and air-fuel or oxygen sensor data at the speed and load where the off-idle lean condition appeared.
- Inspect bank 1 intake plumbing and vacuum hoses for leaks that could admit unmetered air as the throttle opens.
- Check fuel trims on both banks during a controlled off-idle test to determine whether the problem is concentrated on bank 1 or affects the whole engine.
- Measure fuel pressure and delivery under the conditions specified by the manufacturer, since low supply can cause a lean condition as demand rises.
- If air leaks and fuel supply check out, assess bank 1 injectors for restriction and verify sensor response using manufacturer diagnostic procedures.
Common fixes
- Repair a leaking vacuum hose or intake connection affecting bank 1.
- Clean or replace restricted port injectors if testing confirms poor delivery.
- Repair the fuel supply fault if pressure or delivery is below the manufacturer's specification.
- Repair an exhaust leak or replace a sensor only if testing shows it is distorting bank 1 feedback.
Can I keep driving?
You can drive gently for a short distance if there is no stalling or severe loss of power, but avoid heavy loads. A lean mixture can cause overheating or misfires; stop if the engine runs roughly or loses power sharply.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.