Some fuel pressure regulators have ports for a regulator gauge. You can screw the gauge into the regulator and test it. If you don't have one there should be somewhere else along the fuel rail where you can also attach one.
Can a fuel pressure regulator be cleaned?
Do not use compressed air to clean a fuel pressure regulator. If necessary, clean the fuel pressure regulators screen. If the fuel pressure regulator is immersed in a solvent bath, it will be damaged. The pressure regulator should be replaced if the filter screen is contaminated.
What can a bad fuel pressure regulator cause?
A faulty fuel pressure regulator may cause the vehicle to experience misfires, a reduction in power and acceleration, and a drop in fuel efficiency. These symptoms can also be caused by a wide variety of other issues so having the vehicle properly diagnosed is highly recommended.
How do I fix code P0172?