P2A8F: Alternative Fuel Pump B Performance

What it means

The control module monitors alternative fuel pump B’s ability to deliver the required fuel supply. It sets this code when the pump’s performance falls outside the expected range under monitored operating conditions.

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

Alternative fuel pump B supplies fuel to the engine's alternative-fuel system. The control module monitors pump B's delivery and sets P2A8F when its performance falls outside the expected range, which can become more apparent during high demand.

Common causes

Most likely first.

1. Pump internal wear reduces output
2. Fuel filter clogged

Symptoms

• Check engine light on
• Hard start, no start, or stalling under load
• Power loss especially at high load or rpm
• Possible long cranking time

How to diagnose it

1. Record freeze-frame data and review live fuel-system data to note whether pump B performance drops during cranking, acceleration, or high load.
2. Inspect pump B's fuel lines, electrical connector, and nearby wiring for leaks, damage, or loose connections.
3. Check the alternative-fuel filter for restriction and service it if its condition or maintenance interval indicates it is due.
4. Measure pump B's delivery using the vehicle's prescribed test method and compare the result with the manufacturer's specification.
5. If delivery remains low, check pump B's power and ground under load before concluding that the pump itself has failed.

Common fixes

• Replace a clogged alternative-fuel filter.
• Repair damaged wiring or poor electrical connections at pump B.
• Correct a restricted or damaged fuel line to pump B.
• Replace pump B if its output remains below the manufacturer's specification with proper power and ground.

Can I keep driving?

If the engine stalls, is hard to start, or loses power under load, avoid driving in traffic or attempting to overtake; arrange a safe stop if symptoms worsen. Continued use can lead to stalling or a no-start condition.