Damaged, corroded or loose connector or wiring to the tank temperature sensor; Faulty alternative fuel tank temperature sensor; Open circuit or short to ground or supply in the sensor wiring; Water or contamination in the sensor connector or tank-mounted valve assembly; Fault in the alternative fuel control unit or the engine control unit's input circuit; Poorly fitted or incorrectly wired aftermarket conversion.

P01AA

Alternative Fuel Tank Temperature Sensor Circuit.

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
AA: FaultThe specific fault in that area

What it means

P01AA is the generic code for a fault in the alternative fuel tank temperature sensor circuit. The control unit saw a signal from this sensor that was outside the expected range, such as a voltage stuck high or low, an open circuit or a short. The alternative fuel could be LPG, CNG or another gaseous or non-petrol fuel, and the exact sensor location and wiring depend on the vehicle and conversion.

Symptoms

Engine warning light on
Car runs only on petrol, or the alternative fuel mode is unavailable
Fuel gauge or range reading for the alternative fuel looks wrong
Poor running or hesitation while on the alternative fuel
Other alternative fuel system codes stored alongside

Possible causes

Damaged, corroded or loose connector or wiring to the tank temperature sensorlikely
Faulty alternative fuel tank temperature sensorlikely
Open circuit or short to ground or supply in the sensor wiringpossible
Water or contamination in the sensor connector or tank-mounted valve assemblypossible
Fault in the alternative fuel control unit or the engine control unit's input circuitrare
Poorly fitted or incorrectly wired aftermarket conversionrare

How to diagnose

Read all stored codes and freeze frame data, and note whether other alternative fuel codes are present
Check the vehicle's wiring diagram to find where the sensor sits and whether it feeds the engine or a separate alternative fuel control unit
Visually inspect the sensor wiring and connectors for chafing, corrosion, moisture and poor pin tension
Check for any leaks or fuel smell around the alternative fuel tank and fittings, following the safety rules for that fuel
With the sensor connected, view the live tank temperature reading and compare it with the actual ambient or tank temperature
Measure the sensor's resistance against the manufacturer's specification, ideally at a known temperature
Check the sensor circuit for supply, ground and signal integrity, and for shorts or open circuits
Clear the code after repair and retest to confirm it does not return

How to fix

Repair or replace damaged wiring and clean or replace corroded connectors
Replace the tank temperature sensor, or the valve assembly if the sensor is not supplied separately
Dry out and reseal the connector, fixing any source of water ingress
Correct faulty wiring on an aftermarket conversion, using the installer's documentation
Repair or replace the control unit only once all wiring and sensor faults are ruled out

Can I keep driving?

Low severity

The car can usually be driven, often on petrol only, but arrange a diagnosis soon. If you smell fuel or suspect a leak from the alternative fuel system, stop driving and have it checked straight away.

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