What it means
Voltage on the level sensor signal line of alternative fuel tank B is below the expected window. Wire shorted to ground or sensor short.
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-low code sets when the signal voltage is below its expected range, commonly because the signal wire is shorted to ground or the sensor is internally shorted.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- 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
- Check freeze-frame and live AFCM data to confirm tank B's level signal is abnormally low and note whether the gauge or range estimate is affected.
- Inspect the tank B sensor connector and accessible harness for a signal wire rubbed through to ground, corrosion, moisture, or loose terminals.
- Use the wiring diagram to test the signal circuit for a short to ground and check terminal contact against the manufacturer's specification.
- Following service information, isolate the sensor from the harness and check whether the low signal remains to distinguish a wiring short from a sensor fault.
- If the harness is sound, test the tank B level sensor against the manufacturer's specification and replace it if internally shorted.
Common fixes
- Repair a tank B level-sensor signal wire shorted to ground.
- Clean or repair corroded or damaged connector terminals.
- Replace the tank B level sensor if it is internally shorted.
Can I keep driving?
Driving is generally possible if the vehicle runs normally, but the tank B level or range may be wrong, so refuel early rather than relying on the display. The AFCM may limit alternative-fuel operation if it cannot determine the available supply.
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.