P01AB
Alternative Fuel Tank Temperature Sensor Range/Performance.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 1
- AreaFuel and air metering
- AB
- FaultThe specific fault in that area
What it means
P01AB is a generic code meaning the control unit has judged the signal from the alternative fuel tank temperature sensor to be implausible, even though it is still within the sensor's electrical limits. It applies to vehicles that run on a second fuel such as LPG or CNG alongside petrol or diesel. The control unit may have seen a temperature that does not fit the ambient or engine temperature, a reading that is stuck, or one that changes too slowly or erratically. The exact test and the sensor location depend on the vehicle and fuel system.
Symptoms
- Engine warning light on
- Fuel gauge or fuel level reading for the alternative fuel behaving oddly
- Car refusing to switch to the alternative fuel or reverting to petrol or diesel
- Poor running or hesitation while on the alternative fuel
- Inaccurate range estimate or fuel quantity calculation on the alternative fuel
Possible causes
- Faulty or drifting alternative fuel tank temperature sensorlikely
- Damaged wiring, poor connection or corrosion in the sensor circuit (high resistance, intermittent contact)likely
- Sensor reading skewed by its position or contamination, for example moisture or debris at the tank connectorpossible
- Fault in the alternative fuel control unit or tank module that processes the signalpossible
- Real temperature fault, such as an abnormal temperature inside the tank or tank heating or cooling issue, causing a genuine mismatchrare
- Outdated or faulty control unit calibration where the manufacturer has identified one as a known causerare
How to diagnose
- Read all stored and pending codes and note the freeze frame data, including ambient, coolant and fuel temperatures at the time the code set
- Check for any related codes for the alternative fuel system, sensor circuit or other temperature sensors and deal with those first
- Visually inspect the sensor wiring and connectors at the tank for damage, chafing, corrosion, moisture and poor pin tension
- With a scan tool, view the live alternative fuel tank temperature after the car has sat overnight and compare it with ambient and other temperature readings
- Watch the reading while wiggling the harness and connector to look for dropouts or jumps
- Measure the sensor resistance and compare it with the manufacturer's temperature table for the model, and check reference voltage, signal and earth at the connector
- Check for any manufacturer service information or calibration updates for this code on the specific model and fuel system
- Check the tank, its fittings and the alternative fuel system for leaks or faults following the safe procedure for that fuel type
How to fix
- Repair or replace damaged wiring, terminals or connectors in the sensor circuit
- Clean and dry the connector and secure it properly if corrosion or moisture is found
- Replace the alternative fuel tank temperature sensor, or the tank module if the sensor is not supplied separately
- Repair or replace the alternative fuel control unit if the sensor and wiring test good and the fault is confirmed
- Apply a manufacturer calibration update only if service information lists it as a fix for this fault
- Clear the code after repair and road test to confirm it does not return
Can I keep driving?
The car can usually be driven, often on the primary fuel, but get it diagnosed soon because the alternative fuel system may be limited or unreliable. If you smell gas or suspect a leak, stop driving and have it checked straight away.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.