What it means
Voltage on the level sensor signal line of alternative fuel tank B is above the expected window. Wire shorted to B+ or sensor open.
At a glance
- Usually lights the check-engine light
How it works
The AFCM monitors the signal circuit from the level sensor in alternative fuel tank B. This circuit-high code sets when signal voltage is above its expected range, often because the signal wire is shorted to battery voltage or the sensor circuit is open.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open level sensor
- Connector pins corroded - high contact resistance
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
- Review freeze-frame and live AFCM data to confirm tank B's level signal is abnormally high or fixed and check what the gauge displays.
- Inspect the sensor connector and accessible harness for an open wire, backed-out pins, corrosion, or a signal wire contacting a power feed.
- Use the wiring diagram to test the tank B sensor circuit for an open or short to B+ and check terminal contact against the manufacturer's specification.
- Following service information, isolate the sensor from the harness and see whether the high signal remains to narrow the fault to wiring or sensor.
- If the circuit is intact, test the tank B level sensor against the manufacturer's specification and replace it if open.
Common fixes
- Repair an open or signal wire shorted to B+ in the tank B sensor circuit.
- Restore proper contact at loose, corroded, or backed-out connector terminals.
- Replace the tank B level sensor if its element is open.
Can I keep driving?
Driving is generally possible if the vehicle runs normally, but do not trust tank B's displayed level or remaining range and refuel conservatively. Alternative-fuel operation may be limited if the AFCM cannot establish the available fuel level.
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.