What is a Fuel Injection Control Module (FICM)?
Shortly, A fuel injection control module (FICM) is a device that tells the injectors when and how much fuel to deliver to the engine cylinders.
FICM controls the electrical impulses that open and close the fuel injectors, which consist of two halves, the Power Supply and Logic Board.
As is known, fuel is delivered to the engine to mix with the air and generate the power required by the vehicle. Fuel must be introduced into the engine at specific times, and the amount of fuel entering the cylinders is also critical in determining the power the engine produces. While the fuel injectors are responsible for injecting fuel into the engine, the system that dictates the injector’s fuel quantity and injection timing are the FICM (Fuel Injection Control Module).
It is an electronic module that controls and drives the fuel injectors.
FICM consists of two parts:
Power Supply, It generates the voltage that the logic board needs to control the injectors. This is also the most common cause of FICM failure. The FICM power supply is designed to provide 48 volts; when the voltage falls below this requirement, a faulty FICM power supply can be identified.
Effects of low voltage FICM: Incomplete combustion in the engine can result in poor performance and poor fuel economy.
Difficulty starting and running poorly when the engine is cold.
Logic Board, is located in the recessed half of the FICM assembly. The function of the logic board is to convert 12 VDC to 48 VDC. 48 volts is the voltage the logicboard uses to drive the engine injectors.
A malfunctioning FICM can cause starting problems, loss of power, misfires, and poor fuel economy. And your check engine light may be triggered as well. These symptoms are also related to a faulty injector, a faulty fuel pump, or a clogged fuel filter, so make sure to check the condition of the rest of the fuel system.
5 Common Symptoms of FICM found on GM Duramax
Want to know what are the symptoms of Duramax Engine FICM failures? The most common sign you can find is a hard start.
By the time you realize there’s a problem with your FICM, it’s usually too late. But if you watch carefully, you can spot symptoms before it’s too late. The Fuel Injection Control Module (FICM) serves as the power and control provider for the fuel injectors. The power side of the FICM ensures that 48 volts are supplied to the injectors. Without this certain amount of power supply, the fuel supply would be limited and the engine would not start.
However, you can avoid such disasters by paying attention to the signs that bad FICM can cause and taking the necessary steps to prevent them.
Symptoms of failed FICM on Duramax and fix solutions
FICM will show symptoms before it gets completely bad. These symptoms can be diagnosed with professional tools or with the help of a specialist. A bad FICM cannot provide the exact amount of voltage to the injectors. Therefore, the engine takes longer to start. Normally it would start, but it doesn’t seem to start.
Rough engines, misfired injectors and excessive smoke are commonly found on the 2005 Duramax failed FICM.
Injector Misfire
Injector misfires often occur when the engine is started frequently or continuously. It can cause motor sputtering and vehicle body vibration.
The failure of the FICM Logic Board is the cause of this symptom.
Fix Solution
Look for options to fix FICM. If it cannot be repaired, replace the FICM. The new FICM will provide proper fuel injection control and help your vehicle run better.
Power Loss
Failure of the FICM usually causes the engine to lose power. It is often mistakenly thought to be the result of poor injectors.
The FICM must be checked before replacing the injector. Power side disable or damaged Duramax FICM fuse may be the cause of the problem.
Fix Solution
Remove the FICM and replace the power side of the device. Replacing the faulty power side should fix the power loss issue for your vehicle.
Hard to start
No matter how many times you turn the key to start, the engine won’t turn over when it is cold. You don’t know what the problem could be.
Well, one problem may involve the Fuel Injection Control Module (FICM). The FICM has a voltage of 48 volts as it fires the injectors. If the voltage falls too low, the injectors will not fire. You can perform a FICM check to see how much voltage it has.
Fix Solution
It’s best to check the FICM when the engine is cold and you have someone who can help. You should move the coolant reservoir to give you room. You don’t have to fully disconnect the hoses. Just remove the two bolts holding the reservoir to the cowl and push it to the side.
Remove the two screws on the lid of the FICM and take it off. When you look inside, you will either see 4 screw heads or 7 screw heads depending on the year your truck was manufactured. With a multimeter, set it to DC volts and place it on the far right screw if there are only 4 screw heads. When testing 7 screw heads, place the multi-meter on the screw on the far left in the top row of four screws. Never allow the multimeter's probe to touch the case.
Have your assistant turn the engine key without starting the vehicle up. With the key ON, test the voltage. If the voltage is 46 or more, the FICM is fine. If it ever drops below 36, then something is seriously wrong with your FICM.
Tell your assistant to cycle the key as you continue to check the voltage during the key-on buzz test, it should not drop below 46 volts. Turn over the engine and check to see if the FICM maintains its voltage. If it does, your FICM is fine and you can troubleshoot other areas to determine the engine problem.
Excessive Smokes
When the supply voltage is low, the injectors slow down. This can lead to excess power in the exhaust. The timing and duration of fuel injection become messed up, resulting in smoke.
Fix Solution
You can replace the power side of the FICM yourself. This is the most cost-effective way to fix FICM. If this seems impossible, seeking expert advice is the best thing you can do.
Rough Engine
Engine failure is one of the symptoms of a failed FICM relay. After a long period of cranking, the engine finally get started, but the engine was still rough for quite some time.
In some cases, the roughness persisted, making the driving experience uncomfortable.
Fix Solution
Troubleshoot and fix FICM issues with expert help. It will cost you money, but it is more affordable than buying a new FICM.
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