Question about 2004 GMC Sierra 2500
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Posted on Jan 02, 2017
Fuel Rail Pressure Low During Power Enrichment
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, DTCs will be set.
DTC U1000 and U1255 Circuit Description Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within about five seconds of beginning serial data communication, DTC U1000 or U1255 is set. When more than one critical parameter does not have an identification number associated with it, the DTC will only be reported once. The class 2 serial data line on this vehicle is a ring/star configuration. The following modules communicate on the class 2 serial data line:
• The body control module (BCM) • The digital radio reciever • The driver door module (DDM) • The electronic brake control module (EBCM) • The front passenger door module (FPDM) • The HVAC control module • The inflatable restraint sensing and diagnostic module (SDM) • The instrument panel cluster (IPC) • The memory seat module (MSM) • The powertrain control module (PCM) • The radio • The radio amplifier • The rear seat audio (RSA) controller • The rear seat entertainment (RSE) assembly w/U42 • The rear wheel steering control module • The remote playback device-CD player w/U1S • The transfer case shift control module • The transmission control module (TCM) w/Allison transmission • The theft deterrent control module • The vehicle communication interface module (VCIM) w/UE1
Posted on Dec 09, 2008
I see that you had the injectors replaced 20,000 miles ago. I would still check the oil to make sure it is not overfull. The new injectors could be bad. If the oil level is not overfull then get a paper towel and touch the dip stick tip on the paper towel while oil is on the dip stick. If it's only oil it will not spread. If it has diesel in the oil the oil with spread. If this test doesn't show the injectors to be bad then you have three other possibilities. The FICM (fuel injection control module), the fuel pressure regulator, or the injection pump. It's hard to pinpoint what the problem is without running more tests and the only way to run those tests is with the computer the dealership has. Just so you know your injectors are still under warranty until 100,000 miles. Most likely you will have to take it to the dealership to get you truck fixed. I hope this helps you some.
Posted on Jan 05, 2009
SOURCE: 2002 GMC 2500HD Duramax No
TEST the vacuum pump. Both systems are run by it. Pressure should be at least 10psi right out of pump at 1000 rpm.
P.S. If pressure varies more than about 4 psi as the rpm vary the pump is failling.
Posted on Jun 23, 2009
Bulletin No.: 03-06-02-005B
Date: November 18, 2004
Engine Coolant Loss with No Visible Leaks (Reseal Injector Sleeve)
Some owners may comment on engine coolant loss with no visible leaks. Excessive white smoke or a coolant type odor coming from the exhaust pipe, along with low coolant levels, may indicate coolant in the combustion chamber.
Condition may be caused by engine coolant entering the cylinder due to a dirty or damaged seal between the fuel injector sleeve and the cylinder head.
If it's black smoke, you could have a faulty or dirty EGR valve and may not be closing 100%. Remove the EGR valve and clean it with spraying carb cleaner and reinstall after inspecting the valve can move without any binding. Goo luck and hope this helps.
Posted on Jun 25, 2009
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