What it means
Alt fuel tank A level sensor signal voltage below expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The alternative fuel tank A level sensor sends a signal to the control module representing the fuel level. P01B1 sets when the module detects that this signal is lower than its expected electrical range, which can make the indicated level unavailable or inaccurate.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine light on
- Alternative-fuel level reading may be inaccurate or unavailable
- Fuel gauge or range estimate may be unreliable
How to diagnose it
- Save freeze-frame data and check tank A level data for a reading that is implausibly low or unavailable while the code is active.
- Inspect the tank A sensor connector and harness for chafing, water intrusion, pushed-back pins, corrosion, or a signal wire touching ground.
- With the vehicle safely stationary, gently move the accessible tank A harness while monitoring the signal to check for a change that points to an intermittent short or poor connection.
- Check the tank A sensor signal circuit for a short to ground and inspect connector contact quality using the manufacturer's wiring information.
- If the circuit is intact, test the tank A level sensor and its supply and ground circuits against the manufacturer's specification.
Common fixes
- Clean and secure corroded or loose tank A sensor connector pins.
- Repair chafed tank A signal wiring that is shorted to ground.
- Replace the tank A level sensor if it fails the manufacturer's electrical test.
Can I keep driving?
The low signal can make the alternative-fuel level display or range estimate wrong or unavailable. Do not rely on that display to avoid running out of fuel; seek prompt diagnosis if the vehicle also runs poorly.
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.