Damaged, chafed or shorted-to-ground signal wiring to the sensor; Corroded, loose or contaminated sensor connector or terminals; Faulty alternative fuel rail pressure sensor; Open circuit or fault in the sensor 5 volt supply or ground feed; Genuinely low alternative fuel pressure (for example a supply, regulator or pump fault) that the sensor is correctly reporting; Fault inside the control unit that handles the alternative fuel system.

P01A5

Alternative Fuel Rail Pressure Sensor Circuit Low.

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
A5: FaultThe specific fault in that area

What it means

P01A5 means the control unit has seen the signal from the alternative fuel rail pressure sensor (for example on a gas-fuelled or bi-fuel system) fall below the expected voltage range. This points to an electrical fault in the sensor circuit, or a sensor reading abnormally low. The exact sensor location and fuel type depend on the make, model and engine.

Symptoms

Engine warning light on
Poor starting or long cranking when running on the alternative fuel
Loss of power or hesitation under load
Rough idle or misfire on the alternative fuel
Car switching back to petrol or diesel, or refusing to run on the alternative fuel
Poor fuel economy

Possible causes

Damaged, chafed or shorted-to-ground signal wiring to the sensorlikely
Corroded, loose or contaminated sensor connector or terminalslikely
Faulty alternative fuel rail pressure sensorlikely
Open circuit or fault in the sensor 5 volt supply or ground feedpossible
Genuinely low alternative fuel pressure (for example a supply, regulator or pump fault) that the sensor is correctly reportingpossible
Fault inside the control unit that handles the alternative fuel systemrare

How to diagnose

Read all stored codes and freeze frame data, noting fuel type in use, rail pressure, engine speed and load when the code set.
Check for related codes such as sensor supply voltage faults or fuel system pressure faults, and diagnose those first.
Visually inspect the sensor, its connector and the wiring for damage, chafing, heat damage, corrosion or water ingress.
With the ignition on, view live sensor voltage or pressure and compare it to the expected reading for the system. Check that it responds sensibly and does not sit at a fixed low value.
Check the sensor supply voltage and ground at the connector against the manufacturer's data.
Test the signal wire for continuity and for short to ground with the connector and control unit disconnected.
Verify actual alternative fuel pressure with a suitable gauge, following the manufacturer's safe procedure for gas or high-pressure fuel systems.
Wiggle-test the harness while watching live data to find intermittent faults.

How to fix

Repair or replace damaged wiring, and fix any short to ground in the signal circuit.
Clean or replace corroded connectors and terminals, and secure the connector properly.
Replace the alternative fuel rail pressure sensor if it reads incorrectly and the wiring and supply are sound.
Restore the sensor supply or ground feed if it is faulty.
Repair the underlying fuel supply fault, such as a pump, regulator or blockage, if actual pressure is low.
Have the control unit checked or replaced only after all wiring, supply and sensor faults are ruled out.

Can I keep driving?

Medium severity

The car can usually be driven for a short time, often on the standard fuel, but fix the fault soon. Fuel supply or pressure problems on gas systems can affect running, so have it checked promptly and stop if there is any smell of fuel or gas.

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