Open circuit or high resistance in the sensor wiring or connector, such as corrosion or a loose pin; Faulty alternative fuel tank temperature sensor; Sensor signal wire shorted to a voltage supply; Broken or damaged sensor ground wire; Damaged or poorly fitted tank valve or sensor harness, especially on an aftermarket conversion; Fault inside the alternative fuel control unit or engine control unit.

P01AD

Alternative Fuel Tank Temperature 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
AD: FaultThe specific fault in that area

What it means

P01AD means the control unit has seen a signal voltage that is too high from the temperature sensor on the alternative fuel tank, such as an LPG or CNG tank on a bi-fuel or dual-fuel vehicle. A reading this high usually points to an open circuit, a poor connection, a short to supply voltage or a faulty sensor. The unit cannot trust the tank temperature, which it uses to work out the fuel density and quantity. Exact sensor location and strategy depend on the vehicle and the conversion or factory system.

Symptoms

Engine warning light on
Alternative fuel mode unavailable, or the car stays on petrol
Poor running or hesitation when on gas
Inaccurate alternative fuel gauge reading
Hard starting on gas or a fuel changeover that fails

Possible causes

Open circuit or high resistance in the sensor wiring or connector, such as corrosion or a loose pinlikely
Faulty alternative fuel tank temperature sensorlikely
Sensor signal wire shorted to a voltage supplypossible
Broken or damaged sensor ground wirepossible
Damaged or poorly fitted tank valve or sensor harness, especially on an aftermarket conversionpossible
Fault inside the alternative fuel control unit or engine control unitrare

How to diagnose

Read all stored and pending codes and the freeze frame data, and note whether other alternative fuel codes are present.
Check live data for tank temperature. A reading stuck at an extreme, such as very cold or at the limit, suggests an open circuit.
Inspect the sensor, tank valve connector and harness for damage, corrosion, water ingress, chafing and bent or pushed-out pins.
Unplug the sensor and check its resistance against the manufacturer specification at a known temperature, as the value varies by model and system.
With the connector unplugged and the ignition on, check the reference voltage and ground at the harness against the wiring diagram.
Check the signal wire for continuity back to the control unit, and for any short to voltage.
Wiggle the harness while watching live data to find any intermittent fault.
If the wiring and sensor are good, check the control unit supply, grounds and connector, and follow the manufacturer's test procedure.

How to fix

Repair or replace damaged wiring, and clean or replace corroded connectors and terminals.
Replace the alternative fuel tank temperature sensor, or the tank valve assembly if the sensor is not sold separately.
Repair any short to voltage in the signal wire.
Restore a faulty sensor ground connection.
Correct poor harness routing or fitting on an aftermarket installation, using the installer's instructions.
Repair or replace the control unit only after all other causes are ruled out, and have it programmed if required.

Can I keep driving?

Low severity

The car can normally be driven, usually on petrol only, as the fault mainly affects alternative fuel operation. Have it checked soon, because a gas system working without a reliable tank temperature reading is best repaired promptly.

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