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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2002 chevy silverado duramax diagnostic code p1093

Customer Question

2002 chevy silverado duramax diagnostic code p1093
Submitted: 2 years ago.
Category: Chevy
Expert:  SuperDave replied 2 years ago.
Thank you for using Just Answer.I will do my best to answer your question.
P1093:
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 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, DTC will be set.
Conditions For Setting DTC
The difference between commanded fuel pressure and actual fuel pressure is more than 20 MPa; or the FRP Regulator Fuel Flow is more than 15,000 mm3 at 800 RPM, or more than 38,000 mm3 at 2000 RPM.
Conditions For Running DTC
DTCs P0192, P0193 or P1635 are not set.
The ignition is ON.
Diagnostic Aids
This DTC does not set for an idle condition.
A number of conditions may cause DTC P0087 and DTC P1093 to set:
Excessive fuel return to the tank.
A fuel injection pump failure.
A fuel pressure regulator failure.
If you have to prime the fuel system, check for the following conditions:
A restricted fuel supply line.
A fuel supply line air leak.
A sticking Fuel Pressure Regulator may set this DTC.
Customer: replied 2 years ago.
i disconnected the fuel system from truck running off seperate tank and getting air bubbles in the return line replaced fuel lines at cp3 and replaced fuel pressure regulator replaced fuel pressure senor on fuel rail rebuilt primer pump replaced fuel filter and injector balance rates are good
Expert:  Gary replied 2 years ago.
Welcome! My name is ***** ***** I will do my best to assist you with this problem.Ask me about added features such as phone contact anytime if you wish !
was the fuel pressure relief replaced ?
Customer: replied 2 years ago.
Yes
Expert:  Gary replied 2 years ago.
the block assembly with the relief built into it ?
Customer: replied 2 years ago.
Yes replaced
Expert:  GM Tech (Cam) replied 2 years ago.
Hello, I'm Cam.
Can I get your first name please?
I think you may have injector issues. I would like you to do this test. IT cannot be done with a scanner and no values on a scanner will show this issue, thats why this test is vital.
These use hydraulic pressure from the fuel system to operate the injector. SO a small amount of fuel is supposed to bypass to open the main part of the injector to make it operate. When these start to fail, this causes to much fuel to bypass and return to the tank. This resulting fuel loss will lower the fuel rail pressure and at a time when the pressure is needed most, during cranking, it takes longer to build the required 1450 psi to operate the injector. SO the test we do is this. Find the 2 fuel lines on the rear drivers side valve cover. Take the smaller one off and attach your hose to the metal pipe coming from the engine. Put the other end into the container and run the engine to fill that line. Then shut it off and remove the IGN 1 relay from beside the starter relay. If the engine will not start at that time, crank it to fill the line, then empty out the container and keep the line full. Crank the engine for 15 seconds fully and measure the amount of fuel that comes out of that line. More than 24cc means the injectors have failed and they need to be replaced. The code 2 LLY engines can test each injector individually, and the spec is 3ml or 3cc each for the same cranking period.