What it means
The AFCM detects a generic fault on the level sensor of alternative fuel tank B. Tank fill level cannot be displayed or used for range calculation.
At a glance
- Usually lights the check-engine light
How it works
The AFCM uses the level sensor in alternative fuel tank B to estimate the fuel remaining in that tank. This generic circuit fault sets when the module detects an electrical problem with the sensor signal and cannot reliably display the level or calculate remaining range.
Common causes
Most likely first.
- Level sensor failed
- Wiring or connector fault
Symptoms
- Check-engine or alternative-fuel system warning light
- Alternative-fuel tank level or remaining range may be inaccurate
- Alternative-fuel operation may be limited
How to diagnose it
- Read freeze-frame and AFCM data to confirm the fault concerns tank B's level sensor and note the reported level and operating conditions.
- Compare the displayed tank B level with the recent refuelling history and inspect the sensor connector and accessible wiring for looseness, corrosion, or damage.
- Use the vehicle wiring diagram to check the tank B sensor circuit for continuity, shorts, and sound terminal contact against the manufacturer's specification.
- Check whether the AFCM live level reading changes plausibly after a refuelling event or as permitted by the vehicle's service procedure.
- If the wiring is sound but the reading remains absent or implausible, test the tank B level sensor against the manufacturer's specification and replace it if faulty.
Common fixes
- Secure the tank B level-sensor connector.
- Repair damaged wiring or corroded terminals in the tank B sensor circuit.
- Replace the alternative fuel tank B level sensor if it fails testing.
Can I keep driving?
The code mainly makes tank B's level and remaining range unreliable, so do not use the displayed estimate to judge how much alternative fuel remains. Driving is generally possible if the vehicle runs normally, but refuel conservatively and watch for fuel-system warnings.
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.