Level sensor signal wire shorted to a voltage supply; Open circuit or poor connection in the sensor ground or return wire, causing a high signal reading; Faulty tank level sensor or sender, such as a worn track or stuck float; Corroded, damaged or loose connector at the tank or control unit; Damaged wiring harness, chafed or broken near the tank or underbody; Fault in the alternative fuel control unit or its sensor input.

P01B2

Alternative Fuel Tank A Level Sensor Circuit High.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
B2: FaultThe specific fault in that area

What it means

P01B2 means the control unit has seen the signal from the alternative fuel tank 'A' level sensor stay above its expected electrical range. This is a circuit fault, so it points to a short to voltage, an open ground or a faulty sensor rather than a genuinely overfull tank. The alternative fuel type (for example LPG or CNG) and the sensor layout depend on the vehicle.

Symptoms

Engine warning light on
Alternative fuel gauge reading full, stuck, or erratic
Alternative fuel level reading missing or showing a fault
System may revert to petrol or diesel only, depending on the model
Running out of alternative fuel with no warning because the level reading is wrong

Possible causes

Level sensor signal wire shorted to a voltage supplypossible
Open circuit or poor connection in the sensor ground or return wire, causing a high signal readinglikely
Faulty tank level sensor or sender, such as a worn track or stuck floatlikely
Corroded, damaged or loose connector at the tank or control unitlikely
Damaged wiring harness, chafed or broken near the tank or underbodypossible
Fault in the alternative fuel control unit or its sensor inputrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, looking for other alternative fuel or sensor supply faults.
Check live data for the alternative fuel level and sensor voltage, and see whether it is fixed at a high value or changes.
Visually inspect the wiring, connectors and mounting at the tank sensor and control unit for damage, corrosion, water ingress and chafing.
Follow the manufacturer's safety procedure for the alternative fuel system before disconnecting anything at the tank.
With the sensor unplugged, check the reference supply and ground at the harness against the manufacturer's specification.
Check the signal and ground wires for continuity and for shorts to voltage or to each other.
Measure the sensor resistance or output across its range against the manufacturer's data, and compare it to the live reading.
Clear the code after repairs and road test to confirm it does not return.

How to fix

Repair or replace any wiring that is shorted, open or damaged, and secure it clear of sharp edges and heat.
Clean or replace corroded or damaged connectors and terminals.
Repair the sensor ground or return connection if it is open or high resistance.
Replace the alternative fuel level sensor or sender if its readings are out of specification.
Where the supply and wiring are proven good, have the control unit checked and repaired or replaced as the manufacturer advises.

Can I keep driving?

Low severity

The car can usually keep being driven, often on the conventional fuel, but the alternative fuel level reading will be unreliable so do not rely on it. Get it checked soon, and stop if you notice any fuel smell or leak.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.