Today’s diesel engines are complicated. Gone are the days when you could fix your truck on the side of the road with a couple of common hand tools.
Trim codes, or trim files as some may call them, is information that tells your ECM (engine control module) how long the fuel injectors need to stay open.
Without proper trim codes, you could run the chance of rough idle, poor fuel economy, and in some cases, even engine damage. However, the latter is quite rare and seldom happens.
Keep in mind that some engines do not require trim codes to run. But, as with any unknown, always make sure you check the instruction manual.
This article is intended to make sense of what trim codes are, why you need them, and what can happen to your engine if you don’t have them.
Generally speaking, an injector with the same code should have the same flow rate, right? In theory, this is correct, but not all injectors are 100% identical.
We know that each truck will have parts that wear at different rates depending on how it is used. And this applies to injectors as well.
Factors such as magnetic forces, friction, machine tolerances, and so on, all play an important role in fuel injector output rates.
A trim code can adjust the flow of each injector, allowing for a net output that is virtually the same, regardless of wear or mileage. These small differences eventually add up, and not having the right trim code can end up costing you in the long run.
Having the right trim codes is vital to your engine’s performance and installing them can be a simple process if you know what you are doing.
Most injectors should have a serial number stamped on their exterior. This will give you or the mechanic working on your truck all the information required about them.
If you are lucky, the injectors will come with a physical disc containing all the trim information, making things that much easier. The disc’s information would then be uploaded on a computer which in turn would be connected to the truck’s ECM.
Depending on the make and model you own, some of the serial numbers may need to be input manually into a program that then tells the truck’s brain (ECM) the required data for each injector.
As previously mentioned, a trim code is almost certainly a must for injectors that require them from the factory. But how do you find them? In most cases, injectors come with a trim code disc so that they can be programmed in the ECM.
Delphi fuel injectors are the perfect example. Caterpillar C7 and C13 engines come with their own unique trim codes, and DFI supplies each injector with the necessary information via a disc. Normally, a trim code should be physically stamped on each injector so that it can be easy to read for the installer.
Simply put, trim codes should be installed if your injectors came with them from the factory. However, it’s not something that will generally impact performance.
If your injectors come with a trim code from the factory, running the engine without that information will only end up causing problems. It is a necessary evil that needs to be taken into consideration on today’s modern diesel engines.
The saying “if it ain’t broke, don’t fix it” should certainly be used as a motto in these situations. Unless your engine starts acting funny, there is no need to mess with injector trim codes.
Nevertheless, if you are putting in new injectors and you don’t tell the ECM that, you could run into a series of issues. They include, but are not limited to rough idle, power loss, over-fueling or under-fueling, and increased emissions.
To keep you from losing sleep, we are here to tell you that in most cases, trim codes will not noticeably affect your truck’s performance. In fact, we’re willing to bet that most owner-operators don’t even know that injector trim codes existed.
If you have installed new injectors and haven’t noticed a negative effect, leave everything well enough alone.
Fuel injector trim codes are a mystery to most owners and even some experienced shop owners. It is a subject that can cause a lot of doubt and confusion.
This article should help you better understand what injector codes are and how they can be used on your diesel engine.
If you have any other questions related to fuel injector trim codes or engines in general, our experienced, ASE-certified staff is here to help. Give us a call at 1-855-212-3022.
