P008B: Low Pressure Fuel System Pressure - Too High

What it means

The low-pressure fuel pressure is above the expected value. Often caused by a stuck-closed fuel return valve or a faulty pressure regulator.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The low-pressure fuel system supplies fuel ahead of the high-pressure pump, and its pressure is monitored by the control module. P008B sets when that low-side pressure is above the expected range, which can happen if a regulator does not release pressure or the return path is blocked.

Common causes

Most likely first.

1. Pressure regulator stuck closed
2. Return line blocked

Symptoms

• Check engine light on
• Rough running or hesitation
• Reduced engine performance
• Hard starting

How to diagnose it

1. Save freeze-frame data and compare commanded and actual low-pressure fuel readings in live data to confirm when pressure is high.
2. Inspect the low-pressure return line, where fitted, for kinks, crushing, or other visible blockage.
3. Check the regulator and its connector or control wiring for damage, loose terminals, or signs of sticking.
4. Measure low-side pressure using the manufacturer's specified procedure and compare the result with the manufacturer's specification.
5. Test regulator response and pressure-sensor accuracy to distinguish a real pressure problem from an incorrect reading.

Common fixes

• Repair a kinked or blocked low-pressure return line.
• Repair damaged regulator wiring or connector terminals.
• Replace a regulator confirmed stuck or unable to control pressure.
• Replace a pressure sensor if its signal fails the specified accuracy checks.

Can I keep driving?

Limit driving and avoid heavy acceleration if the engine hesitates or runs roughly, since incorrect low-side pressure can affect fuel delivery and emissions. Stop if it stalls or becomes unreliable to control.