What are the Signs of a Bad FICM On a Duramax Engine?

The fuel injection control module (FICM) is an important part of your Duramax engine and if it is experiencing issues this can greatly affect the performance of your vehicle. In this post we will take a look at some of the biggest indicators that the FICM may be failing on your Duramax engine.

What Is an FICM?

The fuel injection control module (FICM) is a component that supplies both power and control information to the fuel injectors. It is mounted on brackets above the valve cover on the driver's side of the vehicle.

On the underside of the FICM there are three electrical connections, one for the engine control module (ECM), and the other two which lead to the 8 fuel injectors. Messages from the ECM pass through the FICM instructing the fuel injectors to release fuel into the engine's cylinders.

The fuel once injected is mixed with air and the combination is ignited using sparks from the spark plugs. This series of small explosions power the pistons which spin the crankshaft and in turn make the drive wheels of the vehicle rotate.

Essentially then the FICM controls the injection of the fuel into the cylinders without which the internal combustion engine will not function. This makes it a very important piece of the vehicle so it is important to be aware of any potential signs of breaking down.

There Will Be Warning Signs

The good news when it comes to the fuel injection control module is that it seldomly will just stop working out of the blue. There are usually signs of an issue developing beforehand which can allow you to get the situation fixed.

Generally when the FICM starts to go bad it starts to struggle to supply power to the fuel injectors. As a result the effects of this become obvious and will alert you to the growing issue.

Truck Struggles To Start

As mentioned the FICM initiates the release of fuel into the cylinders as part of the ignition process. If you experience an issue getting the engine to start up this likely means that one of the three components of ignition are missing.

Either there is no spark, air or fuel entering the cylinders and if it is the fuel then the issue very possibly is the FICM. However we wouldn’t check the FICM first as there are other parts that are earlier in the system that could also be at fault.

We would ascertain that the battery and alternator were both functioning correctly before we started to look toward the FICM as the culprit. If needed the battery and alternator can be replaced and should be as their failure to supply power to the FICM could lead to damage with this component.

Sudden Loss of Power

If the engine suddenly starts to lose power this can be an indication that the combustion process is being disrupted in some way. Cylinders may not be firing which could be an indication of a bad fuel injector.

Although it could be a faulty injector it is important first to make sure the FICM unit is in fact working as it should. There may be an issue with the power side of the unit or a fuse may be to blame. Both the power side and fuses can be easily replaced if needed.

If the FICM is working fine then the next step would be to look at the injectors and replace as needed.

Engine Is Running Roughly

A common symptom of a failing FICM might be signs that the engine is not running as smoothly as it normally would. It may take a few attempts to start and once running may sound and feel rough in operation.

If the engine runs roughly throughout the drive this may be an indication that the cylinders are not all firing as they should and the FICM is not supplying the needed power to run efficiently.

Fuel Injector Misfires

Sputtering of the engine and excessive vibration from the engine can be a sign that the fuel injectors are misfiring. This may be due to insufficient fuel in the cylinder not being enough to ignite fully. A fault such as this may not be power related but more likely connected to the logic side of the FICM.

The logic side sends the messages from the ECM to the fuel injectors and if this information is wrong it can cause injector misfires.

Excessive Exhaust Smoke

This is a visible sign of a failing FICM as you can literally see the dark smoke escaping from your exhaust. This can be caused by a low voltage power supply which in turn makes the fuel injectors work more slowly.

The messed up timing of the fuel injectors leads to poorly burnt fuel and as a result excessive smoking. This can be fixed by determining the source of the low voltage issue which can be the battery or alternator or if it is FICM related then it would be the power side of the part.

Less Common Signs

There are also some other less common signs of an issue with the FICM on your Duramax engine. You may notice a coolant leak beneath or near the part. This is one of the engine systems that needs cooling so a leak could mean problems will soon arise.

Can I Fix the FICM Problem Myself?

The FICM is an important part of the engine but it does work in a relatively simple way so in theory if you have a decent level of mechanical knowledge you might be able to replace any parts of the system that you need to.

If the issue is related to the battery or alternator rather than the FICM these are two parts that are not hugely difficult to replace and the process for replacing the power side of the unit is also easy for those with the right skill level.

As it is an important part however you might want to think twice before trying to fix it yourself. Unless you are fully confident that you can perform the repair you may want to get a professional to do the job. A malfunctioning FICM can lead to bigger engine issues so if you fix it incorrectly you may make matters worse.

Conclusion

The fuel injection control module in the Duramax engine is vital in making sure our engine runs and that we can drive our vehicle. Without the input of this part the fuel injectors would not release fuel into the cylinders and we would not get the combustion needed to run our engine.

There are several signs of a failing FICM and trust me it does give us fair warning so we should heed them. Hopefully this article has given you some idea of what to look out for and how to confirm if the FICM is at fault.

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