Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
There is a Factor Service Bulletin for the following GMC models:
2001-2004 GMC Sierra
2003-2004 GMC Topkick C4500/C5500 Series
GMC Factory Service Bulletin OBDII Code P1093
The cost to diagnose the P1093 GMC code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
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 FRP 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, the Diagnostic Trouble Code (DTC) will be set.
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