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How Do I Know If My Transmission Control Module Is Bad?

How Do I Know If My Transmission Control Module Is Not Good

As we know, any part in your car that has a “module” is sure to be a key component of your vehicle. The electronic control module is basically the computer of the vehicle, while the transmission control module is in control of the shifting, the changing of gears, and the proper working of the engine. If the engine is not working well, this can answer the question of “how do I know if my transmission control module is bad?” 

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Transmission Control Module Function


Aside from the transmission control module’s main responsibility, this control module also has various other functions that are key to the working of your vehicle. 

  • Transmitting Trouble Codes 

The transmission control module sends certain OBD-II codes that show your car’s problems to the computer in your vehicle. If your car happens to detect any malfunction or issues within the transmission, the transmission control module can send the codes. If you wonder how you know if the transmission control module is bad, then your OBD-II codes will not be detected. 


The trouble codes can appear in various forms, like the check engine light coming on and being illuminated on your dashboard or other signs that alert you that something will not be right under the hood of your car and in your engine system. When asking yourself, “how do I know if my transmission control module is bad,” the inability to send trouble codes is a clear sign. 

  • Improves Transmission Performance

These parts are also in charge of improving the quality of smooth shifting in your car and your transmission system’s performance. This means that shifting between gears is smooth, easy for the driver, and does not stress the gears. The lack of stress prevents your car from experiencing wear and tear on the gears and less break down over time. 


The module keeps your transmission in better shape for a longer period of time and requires fewer repairs on your transmission. If your transmission requires extensive repairs quite frequently, this can answer the question of “how do I know if my transmission control module is bad?”

  • Identifies Potential Problems

In addition, the party's ability to send OBD-II codes to the car’s internal computer, like the electronic control module, serves as a good way to identify any potential transmission problems before something goes wrong in your vehicle and damages your engine further. Diagnosing issues can help prevent serious damage that is expensive and requires engine replacement that is very costly and time-intensive. 

Signs of a Failing Transmission Control Module


Now that we know that the transmission control module is a huge component of a vehicle with an automatic transmission system, it is imperative to know the signs and symptoms of a failing or damaged transmission control module. Although your car’s transmission control module should technically never need replacing, if you have a damaged control module, repairs or replacements will be necessary. 


The transmission module is key for communicating information with other systems in your car. Suppose you notice that your vehicle’s internal components are not working correctly and signals are not transmitting between the systems. In that case, this can help answer the question of “how do I know if my transmission control module is bad?”


If you have a problem with this control module, you should have it looked at by a mechanic right away so that you can prevent any further damage to your car’s battery and transmission. As a driver, pay attention to the following signs and symptoms of a bad transmission control module.

  • Check Engine Light

Although your check engine light can turn on for various reasons, if the check engine light illuminates on your dashboard, it can mean several things for your car, including a failing transmission control module. If you have any problems with the shifting and your shifting is rough in addition to the light showing up on your dash, this can answer the question of “how do I know if my transmission control module is bad?”

  • Unpredictable Shifting

Along with the check engine light coming on in your vehicle, there can be unpredictable and erratic shifting in your car if you have a problem with the transmission control module. Since the automatic transmission relies on the transmission control module to shift properly, a bad transmission control module can cause incorrect and unintended shifting. 


Unless you have a manual override option in your car, you will need to go to a mechanic or an auto body shop to have the transmission control module replaced and fix your car before it hurts your engine. If you notice that your engine is also suffering in your vehicle, this provides the answer to the question of “how do I know if my transmission control module is bad?”

  • Issues Shifting into Higher Gears

When you gradually increase your car’s speed, you should notice that your transmission should correctly move into higher gears at the right time so that you can easily drive your car uphill or while accelerating. If this does not happen in your vehicle, you will notice that your car’s engine’s RPM will keep increasing instead of slightly changing during an upshift. 


Since each gear has a max speed that it can reach within the gear, you might never reach the speed necessary, like driving on a highway, if your car will not shift into a higher gear and allow you to drive faster. If your car is having trouble shifting into higher gears to go quicker, then this can answer, “how do I know if my transmission control module is bad?”

  • Problems Downshifting into Lower Gears

This problem is similar when the car has issues shifting into higher gears, but the problem is actually in reverse order. In order to pass a slow-moving vehicle and to shit your transmission, your car will fail to go into a lower gear when you press the pedal to the floor and try to accelerate quickly, whether it be passed a car or up a hill.


If you are cruising down the highway at high speeds, then your transmission should be going into lower speeds when you try to slow down – like when your car comes to a stop, the automatic transmission should be changed into first gear. 

  • Car Stuck in the Same Gear

If your car is unable to shift out of first gear and know that your transmission control module is bad, your car will stick in neutral or first gear. This means that the transmission will not shift and you will not be able to move the car anywhere. If you find that your car is unable to drive or move anywhere, this can answer the question of “how do I know if my transmission control module is bad?”


There are many reasons why it may be difficult or hard to shift gears, whether in automatic or manual transmission.  If you are having a hard time shifting gears in manual transmission, this could be due to your transmission stuck in a particular gear. This problem is generally caused by a few issues and can usually indicate the following problems in your car: 


  • Low oil level or the wrong type of oil for your specific car and transmission
  • Problems with the linkage or the shifter – if this is the case, search for any damage to the internal rods, control arm bushings, or the shifter arms.
  • Internal components like the forks or synchronizer sleeve stuck.
  • Worn-out or damaged drive gear teeth, regarding the hub sleeve, hub gear, or gears themselves
  • Stuck shift rail
  • Misaligned transmission


Any of these indications can answer the question of “how do I know if my transmission control module is going bad?”

  • Delayed Shifting

In order to be able to change gears and speeds of your car, your transmission control module has to cycle through various gears at the time it is necessary. If you have a bad transmission control module, then this can cause the cycle between gear to move too slowly. Delayed shifting can cause poor acceleration and cause the performance of the engine to be suboptimal. 


When you approach a hill or pull heavy loads, the shifting performance can worsen, showing you how you know your transmission control module is bad.

  • Reduced Fuel Economy

If you experience problems with your transmission system and your transmission control module, this can result in low fuel economy and poor fuel mileage. An automatic transmission is designated for quick and smooth gear selection and timing, providing you with the best possible fuel economy and the most efficient gas mileage. 


If you have a transmission control module that has gone bad or is damaged, this can affect the timing and your engine will have to overheat and work harder than usual to give the same amount of performance. This can cause you to spend more fuel than usual, more money filling your tank, and answer the question “how do I know if my transmission control module is bad?”

Transmission Control Module Replacement Cost


In order to replace the transmission control module if it is not working correctly or has been damaged over time, the replacement cost of a transmission control module ranges anywhere from $500 to $900. To determine how you know your transmission control module is bad, you will need to repair or replace the module. The parts costs will be around $450 to $700, while the labor costs will be between $50 and $200 in total. 

  • Repair Cost

Sometimes, the damage is not high enough to warrant a full replacement for the transmission control module, and you will just need to do the repair. Another option is to repair your TCM with the transmission control module repair cost lower than replacing it. On average, you can expect to pay around $300 to repair your transmission control module. While most TCM repair businesses will offer a warranty, it can be a real problem if the repair is not done right since you will have to pay for the replacement. 

  • Transmission Repair

The transmission replacement is easily one of the most extensive and expensive replacements and jobs. The average cost of the transmission replacement typically ranges from around $1,800 to $3,400 for most cars. If you decide to save some money, a used transmission ranges from about $800 to $1,500, while a rebuilt transmission charges between $1,100 to $2,800, and a remanufactured option runs between $1,300 and $1,300. 


If your car is old, you might expect to pay a different amount than if your car is new. An older car might have more issues and require a higher replacement or repair cost. The car will also have been through more wear and tear, leading to a more extensive repair job. An older car might often make it harder for the driver to shift gears in the manual transmission. 

  • Repairs Related to the TCM Replacement

Along with the replacement of the transmission control module, if your TCM has gone bad, some other repairs are directly related to this issue. The air conditioning refrigerant line replacement runs between $561 and $591, and the alternator replacement runs between $572 and $760. 


The last three repairs for the car that are related to the transmission control module replacement are the camshaft seal replacement for between $368 and $477, the variable valve timing actuator replacement for around $806 and $967, and the sliding door lock actuator replacement between $260 and $283. 


As you can see, the transmission control module is a key part of your vehicle, helping all of the other internal parts work smoothly and effectively. If this part is not operating at a high level, it can cause further issues with the engine, fuel system, and transmission. 


In order to figure out and diagnose the issues with the TCM, you need to keep an eye out for issues shifting, problems getting into high and lower gears, performance declines, reduced fuel economy, and the check engine light on your dashboard. Noticing these warning signs can help you prevent needing to answer the question, “how do I know if my transmission control module is bad?” 


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