P0087: OBD-II code P0087 means the fuel rail pressure is below what the PCM commanded — the engine is starved of fuel under load, especially on GDI and diesel engines.

Symptoms

• The check engine light is illuminated and the engine may enter reduced-power (limp) mode under acceleration.
• Extended cranking, hard starting, or sudden stalling under load because the engine cannot get enough fuel to the injectors.
• Rough running, misfires, and a noticeable loss of power on hills or during hard acceleration.

Common causes

• A weak or failing low-pressure lift pump inside the fuel tank that cannot supply the high-pressure pump adequately.
• A worn high-pressure fuel pump (HPFP) on GDI or common-rail diesel engines — a very common failure at higher mileage.
• A clogged fuel filter, a leaking fuel injector, or a stuck-open fuel pressure regulator bleeding pressure back to the tank.

What to do?

Read live fuel rail pressure data during a road test — actual pressure should closely track commanded. Check low-pressure fuel supply at idle and under acceleration with a mechanical gauge. Replace the fuel filter first (cheap, easy). If pressure sags under load, test the lift pump; if HPFP output is low, replace it. Inspect the rail and injectors for leaks.