What it means
The AFCM detects that alternative fuel consumption exceeds the expected value for the active operating mode. Indicates injector leakage, fuel pressure too high, or unmetered fuel loss.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The alternative fuel control module estimates fuel use for the active operating mode and compares it with expected consumption. P2BB1 sets when consumption is higher than expected, which can result from a leaking alternative-fuel injector, excessive rail pressure, or fuel escaping without being properly metered.
Common causes
Most likely first.
- Alt fuel injector leaking
- Fuel rail pressure above target
Symptoms
- Check-engine light
- Reduced fuel economy
- Fuel odor
How to diagnose it
- Review freeze-frame and live fuel-mode data to confirm the high consumption occurred while alternative fuel was selected.
- Check for related fuel-pressure, injector, or fuel-switching codes before testing individual parts.
- With the engine off and using the vehicle's safety procedure, inspect alternative-fuel lines, rail, and injector connections for signs of leakage.
- Compare alternative-fuel rail pressure with the manufacturer's specification and check whether it holds as specified after shutdown.
- Test injector sealing and delivery using the approved procedure for the vehicle's alternative-fuel system.
Common fixes
- Repair a confirmed leak at an alternative-fuel line or connection.
- Replace a leaking alternative-fuel injector.
- Repair the pressure regulator or control fault if rail pressure is above specification.
- Correct any verified fuel-metering or tank-fill correction issue.
Can I keep driving?
If you smell fuel, stop the engine, move away from the vehicle, and have the leak checked before driving because leaked fuel can create a fire risk. Without a fuel odor, avoid unnecessary trips until excessive consumption is diagnosed.
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.