What it means
The control module monitors pressure in the alternative fuel rail or system. It sets this code when pressure falls below the expected operating range.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The alternative-fuel pressure system supplies fuel at a usable pressure, and the control module monitors pressure reported for the rail or system. P01A8 sets when that pressure is below the expected operating range, which can leave the engine short of alternative fuel.
Common causes
Most likely first.
- Low alternative-fuel supply or an empty tank
- Weak or failing fuel pump
- Restricted fuel filter or line
- Pressure regulator fault
Symptoms
- Check-engine light on
- Hard starting or extended cranking
- Poor acceleration or reduced power
- Engine may stumble or stall
How to diagnose it
- Record freeze-frame data and check live alternative-fuel pressure during cranking and running to confirm when the pressure falls below range.
- Check the alternative-fuel tank level and confirm the vehicle is actually operating from that fuel supply.
- Inspect the fuel lines, filter area, and electrical connections for visible damage, leaks, or disconnected wiring, taking appropriate fuel-system precautions.
- Check for restrictions in the alternative-fuel filter or lines and verify pump power and ground during the pressure fault.
- Measure system pressure and assess the pump and regulator against the manufacturer's specification.
Common fixes
- Refill the alternative-fuel tank if its supply is low.
- Replace a restricted alternative-fuel filter or repair a restricted line.
- Repair poor pump electrical connections or damaged wiring.
- Replace a weak pump or faulty pressure regulator after confirming pressure is below specification.
Can I keep driving?
Avoid driving if the engine is hard to start, loses power, stumbles, or stalls; low alternative-fuel pressure can leave you stranded and may cause unsafe loss of power in traffic. Have the pressure fault diagnosed before relying on the vehicle.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.