How To Test Your ECM Computer

Visual Inspection of the Control Module ECM When inspecting your control modules on your vehicle it is important to be conscious of any physical defects you may come across such as frayed wires or corrosion without the need to visit an auto repair shop. Oftentimes, a faulty ECM can be a result of a burnt circuit board due to poor wiring or other electrical mishaps. Some vehicles are notorious for their engine computer’s tendency to become fried due to faulty spark plugs. Performing a visual inspection is something that anyone can do right from home and is one of the first tests you should perform if a faulty ECM is suspected as ECM plays a very serious role in your vehicle.

You should first take out the ECM to make sure the pins are in an upright position and check inside the plug and casing to make sure there is no corrosion for all wire connection . At this point a smell test should be performed, if the plug emits a distinct odor like burnt electronics then there is a good chance the internal circuit board is fried. You can also check to see if the unit is burnt by opening the unit and inspecting the circuit board to see if there are any fried components. If you find any corrosion or burnt components on your unit then a replacement is required and further diagnosis will need to be done to determine the cause of the burnt unit or corrosion.

Engine Control Modules Swap

On older vehicles, typically models 1995 and older, switching your ECM for another unit is a sufficient mode of testing. Because OBD-I engine computers do not require programming upon installation, they will start and run your vehicle once installed. In order to find a suitable replacement, you need to locate the part number on your original unit and find a replacement with a part number that matches. Once installed, drive your vehicle for a complete drive cycle to ensure the issues you were experiencing with your original unit do not return. If the issues do not return after test driving the vehicle then that is a good indicator that there was an issue with your original unit. It’s important to remember that this test will only work on vehicles with computers that don’t require programming which would rule out all newer model vehicles.

Using a Scanner and Process of Elimination

One of the most important functions of an ECM is its ability to alert the driver when there is an issue with the vehicle. Whenever your vehicle’s check engine light comes on there will be fault codes attached to it that will indicate to the driver what the possible issue might be. In order to get those codes you will need to plug your scanner into the OBD-II port and from there it will notify you of any codes which are provided by the ECM so you can perform the proper diagnostic test. If your ECM is faulty then it will often throw codes for modules that are not faulty or will continue to throw codes for a faulty part even after that part is replaced. Analyzing an error code is not always an exact science but is an important starting point when diagnosing your vehicle as it can help you diagnose the right issue for example identifying that the issue was the control modules and not the electrical system .

Once you have determined the codes you want to use process of elimination to deduce whether the computer is at fault. The best way for a deduction to be made is by making sure that all the sensors and actuators are functioning properly; we need to ensure that the sensors are supplying the correct amount of power to the ECM and that all components are able to receive the correct signals that the computer provides. We can do this by tracing the voltage through each component. Components that provide power such as the battery, ignition switch, and the fuses are called inputs while components that receive data such as spark plugs, fuel injectors, and the starter are called outputs. First we want to ensure the battery is providing the correct amount of voltage and trace that voltage all the way from the battery, through the sensors, to the engine computer. If there is a problem with the engine computer then it will not process the data correctly and it will affect the way the outputs function. This may result in misfires, the fuel pump not coming on, a lack of spark, etc. Simply stated, if all inputs and outputs are in working order then you know the problem is a result of the way the computer itself is processing the data.

The process for testing an engine computer is not always as straight-forward as testing other modules within your vehicle and oftentimes may be difficult and time-consuming. While other components may normally display clear-cut symptoms when faulty, symptoms within your engine computer may not be as obvious. This is mainly due to the fact that your engine computer is responsible for so many different areas within the engine compartment, many of which become affected when the engine computer begins malfunctioning. A faulty ECM may also display similar symptoms as other faulty components making it difficult to determine where the symptoms originate.


The primary purpose of the engine computer is to ensure that your vehicle is running smoothly and efficiently. It does this by analyzing the data it receives from individual sensors and transmitting that data to a variety of actuators that will adjust the way they perform based on the communicated information. When it comes to determining if your ECM is faulty, the goal is to make sure that there is an issue within the computer itself- that there is an issue with how the ECM is processing the data and not an issue with the sensors sending the data or an issue with the actuators receiving the data. In addition to being time-consuming, replacing your ECM can be costly so it is important to be sure your vehicle’s problem truly lies within the ECM. While sending your ECM to a professional is the only sure-fire way to receive a guaranteed diagnosis, there are steps you can take in order to ensure you are making an informed and sensible decision to have your unit replaced. The same way that wear and tear on mechanics happens over a period of time, strain can also as efficiently as possible.

As technology becomes more developed, companies becoming more reliant on electronics to control different aspects of the modern vehicle. Components that used to be controlled manually are now controlled by sophisticated computers

The process for testing a car computer is not always as straight-forward as testing other modules within your vehicle and oftentimes may be difficult and time-consuming. While other components may normally display clear-cut symptoms when faulty, symptoms within your engine computer may not be as obvious. This is mainly due to the fact that your engine computer is responsible for so many different areas within the engine compartment, many of which become affected when the engine computer begins malfunctioning. Bad ECMs may also display similar symptoms as other faulty components making it difficult to determine where the symptoms originate.


The primary purpose of the engine computer is to ensure that your vehicle is running smoothly and efficiently. It does this by analyzing the data it receives from individual sensors and transmitting that data to a variety of actuators that will adjust the way they perform based on the communicated information. When it comes to determining if your control modules ECM is faulty, the goal is to make sure that there is an issue within the computer itself- that there is an issue with how the ECM ( Engine control modules ) is processing the data and not an issue with the sensors sending the data or an issue with the actuators receiving the data.

In addition to being time-consuming, replacing your bad ECMs can be costly so it is important to be sure your vehicle’s problem truly lies within the ECM. I reset and test my ECM after every new major install and so should you. A failing engine control module is not something that should be taken lightly, your vehicle will perform on reduced power, your plug wires could be causing a short to the ECM so be sure to check them! Whether you are getting a trouble code, your fuel economy is declining, your vehicle stall or misfire , a check engine light or non existent engine performance you should always think the ECM could be the culprit and you do not really need an auto repair shop to do the basic steps


saturn  engine control module
How To Test Your ECM Computer

Flagship One Inc, is the world leader of engine control module repairs, programming and testing, feel free to contact us if you have any question or concerns.

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