Possible causes

– Faulty fuel pump
– Blocked fuel filter
– Faulty fuel pressure sensor
– Fuel pressure sensor harness is open or shorted
– Fuel pressure sensor electrical circuit poor connection
– Faulty Fuel injector

Tech notes

There is a factory service bulletin for the P0087 Code. The bulletin suggest for replacing the injectors to repair the problem.

The factory service bulletin affects the following models:

2001-2004 GMC Sierra
2003-2004 GMC Topkick C4500/C5500 Series

When is the code detected?

The Engine Control Module (ECM) has determined that the fuel rail pressure is too low for a specific engine RPM

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0087 GMC Description

The engine control module (ECM) uses the fuel rail pressure (FRP) sensor to determine fuel pressure to the fuel injectors. This is then compared to the calculated target fuel pressure as determined by the ECM. The ECM adjusts the fuel rail pressure by modulating the duty cycle of the control driver of the fuel pressure regulator. Injector pulse duration is determined by the measured rail pressure and the target injection fuel into each cylinder. If a sensor circuit malfunction is detected, or the commanded fuel injection pump flow is not within the proper range for a given engine load and speed, DTCs will be set.

GMC Technical Service Bulletins for P0087 code