P01A6
Alternative Fuel Rail Pressure Sensor Circuit High.
- 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
- A6
- FaultThe specific fault in that area
What it means
P01A6 means the control unit has seen the signal voltage from the alternative fuel rail pressure sensor sit higher than its expected range. The alternative fuel system is typically a second fuel such as gas on a bi-fuel or dual-fuel vehicle, but the exact layout depends on the model and conversion. The fault is usually a wiring, supply or sensor problem, but it can also be a real over-pressure condition.
Symptoms
- Engine warning light on
- Car stays on petrol or the main fuel, or will not switch to the alternative fuel
- Poor running, hesitation or reduced power on the alternative fuel
- Hard starting or rough idle
- Higher fuel consumption
- Limp mode or restricted output on some models
Possible causes
- Open circuit or high-resistance fault in the sensor signal wire, or the signal wire shorted to a voltage supplylikely
- Faulty alternative fuel rail pressure sensor reading high or stucklikely
- Poor sensor ground connection or damaged earth wire, which pushes the signal voltage uplikely
- Corroded, damaged or loose connector terminals at the sensor or control unitpossible
- Real over-pressure in the alternative fuel rail due to a regulator or pressure control faultpossible
- Fault in the alternative fuel control unit or main engine control unitrare
How to diagnose
- Read all stored and pending codes and note the freeze frame data, including fuel type in use, rail pressure and engine load.
- Check for other related codes, such as sensor supply voltage, ground or alternative fuel system faults, and deal with those first.
- Inspect the sensor, connector and wiring for damage, chafing, heat damage, corrosion, water ingress and loose pins.
- With the ignition on, view the live rail pressure reading and compare it with the expected value. A reading stuck at maximum suggests a circuit fault.
- Unplug the sensor and check the reference supply and ground against the wiring diagram for your model, then check for a short to voltage on the signal wire.
- Check wiring continuity and resistance between the sensor and control unit, and look for a short to supply or an open ground.
- Compare the sensor reading with a reliable gauge reading on the rail to rule out real over-pressure.
- If the wiring and sensor are good, check the pressure regulator and control unit according to the manufacturer's procedure for the system fitted.
How to fix
- Repair or replace damaged wiring, and clear any short to voltage or open circuit on the signal or ground wire.
- Clean or repair the connector terminals, or replace the connector if it is corroded or loose.
- Replace the alternative fuel rail pressure sensor if it is faulty or reads high with a good circuit.
- Repair or replace the pressure regulator or control components if the rail pressure is genuinely too high.
- Repair or replace the control unit only after all other causes are ruled out, and follow the manufacturer's coding procedure.
Can I keep driving?
The car can usually be driven on the main fuel, but have it checked soon. If there is a smell of fuel, a gas leak or noticeably rough running, stop driving and have it inspected, as an over-pressure fault on a gaseous fuel system can be unsafe.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.