Loose, corroded or damaged connector at the tank pressure sensor; Chafed, broken or intermittently shorting wiring between the sensor and control unit; Failing tank pressure sensor giving erratic output; Poor sensor supply voltage or earth caused by a wiring or fuse fault; Actual pressure fluctuation from a regulator, valve or gas leak fault in the alternative fuel system; Internal fault in the alternative fuel control unit or engine control unit.

P01A2

Alternative Fuel Tank A Pressure Sensor Circuit Intermittent/Erratic.

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
A2: FaultThe specific fault in that area

What it means

P01A2 means the engine control unit has seen an intermittent or erratic signal from the pressure sensor on alternative fuel tank A, such as a CNG, LPG or similar gaseous fuel tank. The reading jumps, drops out or does not make sense compared with expected values or other sensors. The fault is not constant, so it can come and go.

Symptoms

Warning light on, possibly with an alternative fuel system warning
Fuel gauge or tank pressure reading jumping about or dropping to zero
Vehicle switching from alternative fuel to petrol or diesel (bi-fuel) without being asked
Hesitation, poor running or reduced power on alternative fuel
Difficulty starting on alternative fuel
Fault appearing only after vibration, bumps or refuelling

Possible causes

Loose, corroded or damaged connector at the tank pressure sensorlikely
Chafed, broken or intermittently shorting wiring between the sensor and control unitlikely
Failing tank pressure sensor giving erratic outputlikely
Poor sensor supply voltage or earth caused by a wiring or fuse faultpossible
Actual pressure fluctuation from a regulator, valve or gas leak fault in the alternative fuel systempossible
Internal fault in the alternative fuel control unit or engine control unitrare

How to diagnose

Read all stored codes and freeze frame data, noting when the fault set and whether other alternative fuel codes are present, then check the code history for repeat occurrences
Check for any smell of gas and inspect the tank, lines and fittings visually for damage or leaks before going further, following the safety procedure for the specific fuel type
Inspect the sensor connector and wiring along its route for corrosion, bent pins, chafing, water ingress and heat damage
Watch the live tank pressure reading while gently wiggling the connector and harness to see whether the signal drops out or jumps
Compare the live reading with the expected pressure for the tank condition and with any other pressure or temperature data the system provides
Check the sensor supply, signal and earth with a multimeter against the manufacturer's specification, as values depend on the model and system
Check related fuses, relays and earth connections for the alternative fuel system
Check for technical service bulletins or software updates for the specific vehicle and system

How to fix

Clean, repair or replace the faulty connector or terminals
Repair or replace damaged wiring and secure the harness away from heat and rubbing
Replace the tank pressure sensor if its output is erratic or out of specification, using the correct part for the system
Restore faulty supply or earth connections
Repair any fault found in the regulator, valve or fuel lines by a person qualified to work on alternative fuel systems
Update or replace the control unit only if testing confirms a fault or a known software issue

Can I keep driving?

Medium severity

If the car is bi-fuel and runs normally on petrol, it can usually be driven on that fuel until repaired. If you smell gas or the system behaves oddly, stop, keep clear of ignition sources and have it checked by a qualified specialist.

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