When to Replace your Engine Control Module

If you have ever had to go through the daunting process of diagnosing your vehicle’s electrical issues then you have likely heard the term “brain box” in reference to the engine computer. This term is synonymous with the engine computer because in a simple sense, that is essentially what the engine computer is; the brain of your vehicle. The ECM (Engine control module) responsible for making sure that everything in your vehicle is functioning properly, and like the brain, the ECM will communicate with other modules in your vehicle to regulate the way they perform. A functioning ECM will send signals to other modules in order to manage the way they are performing, and in turn, they will send signals back to the ECM to confirm that everything is in working order we can go on a deeper level to name some of the functionailty that relies on an engine control module. The power train control module checks on the airfuel ratio for engines performance / engine load, position sensor, fuel efficiency ,ignition timing and fuel pump If there is any sort of electrical issue, then your ECM will generate a series of fault codes to indicate that there is something wrong which can then be analyzed to determine where the issue lies. This makes the functionality of your engine computer essential to the performance of your vehicle.

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Because the ECM is responsible for the functionality of the engine management system, when it is not working properly it puts the rest of the control units at risk, just to name a few like the oxygen sensors,throttle bodies,flow sensors. Components like the charging system, transmission, emission controls, and other onboard electric modules could all be affected by a faulty ECM. At times you may experience what appears to be an issue with a specific component when the issue really lies within the engine computer or vice versa. Since all of these components communicate with each other and are connected through an intricate wiring system it can make diagnosing your vehicle difficult, frustrating, and time consuming but making a careful diagnosis is extremely important. The following sections will hopefully make it easier to better understand the way an auto engine computer works and act as a guide on when a replacement ECM is necessary.

JEep Engine control Module
Example of an Engine Control Module

Unnecessary Return of Your Engine Control Module

Before making the decision to replace your powertrain control module ( PCM) it’s important to make a thorough and complete diagnosis to make sure that a replacement is truly necessary. Because the engine computer operates through an intricate wiring system and communicates with a series of other modules, it is difficult to diagnose the engine computer based on symptoms alone. Oftentimes what may seem like an engine computer problem is really a wiring issue or an issue with another module altogether. More often than not, units that are sent back to the seller are returned with no faults in them whatsoever. Testing your vehicle’s engine computer is difficult to do when it’s still on the vehicle but there are steps you can take to help make a more accurate diagnosis. Visually inspect your engine control modules to make sure that all the pins are upright and make sure that your unit does not smell burnt. You can also open the ECM up to make sure there are no burnt components on the circuit board. You also want to utilize an OBD scanner to scan your ECM for any codes. From there you can analyze these codes to determine if any modules need to be replaced. Finally, you can perform a voltage drop test to ensure that your ECM is receiving the proper voltage from the ignition switch, fuses, and sensors. Performing these steps will assist in narrowing down the issue to the ECM and from there you can send the unit back for testing and replacement. The ECM replacement process is not a too difficult task some might say.

Why Did it Die?

Among the most common causes of PCM failure is a burnt circuit board as a result of shorts and environmental factors such as corrosion. It is important to know these factors when replacing your ECM especially if you have previously had a failed unit. While a burnt or corroded unit requires a whole new replacement it is essential to recognize the causes of these failures in order to ensure they don’t happen again with your new replacement unit. If your previous unit has burnt out then it is necessary to figure out the cause of the short in the circuit board and have it repaired or else you may risk burning out the new unit as well. Typically the cause of the short lies within a shorted solenoid or actuator which must be found and repaired and in some vehicles the short is a result of faulty spark plugs or coils. In order to avoid a damaged ECM from environmental factors the main thing to avoid is water damage. While engine computers are built to withstand the elements, some wear and tear over a long period of time is still possible. It is important to consider these factors especially when returning your unit under warranty as most sellers list electrical damage and water damage as exceptions under their return policies.

Accurate Identification

The first step when replacing your unit is finding the exact unit that is necessary for your vehicle. Most manufactures make dozens of different units for each vehicle and not all of these units are compatible with each other. There are slight differences between each unit but it is essential that you find the exact unit required based on your individual specifications. Most of the time you are not able to determine the unit your vehicle needs based on engine size and fuel type alone, part numbers differ based on information that is not so easily attainable. Most engine computers look exactly the same from the outside, so the best way to identify your unit is by part number.

Once you have determined the engine control unit is necessary for your vehicle then you can move on to reprogramming that unit. It is a common misconception from auto repair shops that engine computers of the same part number are interchangeable with one another. If you are replacing your engine control module ecm with another unit, regardless of whether that vehicle is the exact same one as yours, it must be reprogrammed after installation. There are many companies that will program your replacement unit to your VIN before shipping the unit to you, but regardless, your replacement unit must be programmed to match your Automobile’s VIN ( Vehicle Identification Number ) . This gives your replacement unit the ability to communicate with the other modules within that vehicle.

Replacing a remanufactured PCM

When purchasing a replacement unit from a seller outside of a dealership you will most likely come across “remanufactured” units. A remanufactured Engine control module is a good working module that has had all its faulty components replaced. Sellers will also rebuild these units so that common components that are known to fail have also been replaced. After rebuilding these modules, sellers will put them through extensive testing to ensure that everything is in working order. Normally remanufactured modules are sold directly from stock however, if a particular part number is unavailable, most sellers will offer to repair your faulty unit. Typically repairs remain at a fixed price regardless of availability and still come with a warranty. It should be considered that there are some cases where the module is irreparable and the only way to move forward is with a whole new replacement.

Control Unit Replacement Tips

Replacing your ECU ( engine control unit) is fairly easy and can usually be done without the help of a mechanic regardless of how little experience you have. The location of the control systems differs from vehicle to vehicle but most engine computers are located in the engine compartment or behind components in the instrument panel. When installing your unit the first thing to remember is to disconnect the battery prior to removing the old unit. The battery should only be reconnected once the replacement engine control module ecm has been installed. check on the electronic throttle while you’re at it. Once installed, the ECM will undergo a relearning procedure. For some vehicles, like Ford and GM, you will need to follow a key relearn process to sync your ignition keys to your ECM before your vehicle will start,also pay attention to the intake stroke, the valve timing . As you drive, check if it is reading the right amount of fuel while your ECM will adjust itself to the different nuances of your vehicle. Different vehicles have different requirements to indicate how long you should drive your vehicle in order for your car engines to adjust itself but a general rule of thumb is to complete a drive cycle going over 35mph. Normally after driving 50 miles just like it after a scheduled maintenance you will want to make sure that the check engine light does not come back on even at idle speed, if it does come back on then that may indicate that the problem has not been fixed and that is a nightmare for all car owners, so back to the drawing board and good luck with your ecm replacement process. Visit our store Flagship One we can help.

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