The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Some links on this page are affiliate links: if you buy through them we may earn a commission, at no extra cost to you.
Your vehicle has several efficient systems that make it work the way it does. These systems need to work in collaboration at the same time to ensure the car drives the way you want it to. The transmission control module, or TCM, is an integral part of the communications system. It relays messages between the various systems to identify the different settings your transmission needs to use.
The TCM is also responsible for maintaining a close eye on the car’s transmission to ensure it works as intended at all times. These are two very big responsibilities, which makes TCM one of your engine’s most important components. Your transmission control module should be capable of firing on all engine cylinders while you are driving. This is the only way it can take care of things responsible for keeping your transmission in good shape.
Sometimes, the minor hiccups in a TCM can result in your transmission sustaining damage or running inefficiently. This is why you need to check on the device from time to time to see whether it requires repair or replacement. This guide will walk you through the various signs and symptoms of a faulty transmission control module and the steps you can take to fix it.
Free tools Windows power users keep installed
One-click scans. No signup required.
Signs Your Transmission Control Module Is Not Working
1. Check Engine Light is Always Lit
The check engine light can be lit for extended periods for a wide variety of reasons. It can also mean that your transmission control module is failing. You would know there is something wrong, particularly if you have trouble shifting gears with the light showing on in the dash.
#1 Best Overall
- [Easy to Use—Work Out of the Box] + [FOXWELL 2026 New Version] FOXWELL NT604 Elite scan tool is the 2026 new version from FOXWELL, designed for car owners who want to figure out the cause of issues before fixing car problems by scanning common systems like ABS, SRS, engine, and transmission. The NT604 Elite obd2 scanner diagnostic tool comes with the latest software—no need to waste time downloading software first. Plug the scanner into the OBDII port with OBDII cable to start the diagnosis.
- [Affordable] + [Reliable Car Health Monitor] Will you be confused what happens when the warning light of ABS/SRS/transmission/check engine flashes? Instead of taking your cars to dealership, this FOXWELL scanner will help you do a thorough scanning and detection for your cars and pinpoint the root cause. Note：The device is a diagnostic tool, not a repair tool. To turn off a warning light, you must first physically repair the issue causing it. Only then can the scanner be used to clear the corresponding fault code.
- [5 in 1 Car Diagnostic Scanner] Compared with obd scanners (50-100), NT604 Elite code scanner not only includes their OBDII diagnosis but also serves as ABS/SRS scanner, transmission and check engine code reader. When it’s an odb2 scanner, you can use it to check if your car is ready for annual test through I/M readiness menu. In addition, live data stream, built-in DTC library, data play back and print, all these features are a big plus for it. Note: doesn't support maintenance functions like reset or relearn. For the SRS system, NT604 Elite can read and clear common fault codes not caused by a crash, but crash/collision data cannot be cleared.
- [Fantastic AUTOVIN] + [No extra software fee] Through the AUTOVIN menu, this NT604 Elite car scanner allows you to get your V-IN and vehicle info rapidly, no need to take time to find your V-IN and input one by one. What's more, the NT604 Elite ABS SRS scanner supports 60+ car brands from worldwide (America/Asia/Europe). You don’t need to pay extra software fee. AUTOVIN may not work on some older vehicles or certain vehicle brands. If AUTOVIN fails, please input the vin code manually or go to the Diagnostic Menu to select your vehicle model.
- [Solid protective case KO plastic carrying bag] + [Lifetime update] Almost all same price-level car scanner diagnostic tool only offers plastic bag to hold the scanner.However, NT604 Elite automotive scanner is equipped with solid protective case, preventing your obd2 scanner from damage. Then you don’t need to pay extra money to buy a solid toolbox.
Other reasons for check engine light in addition to the transmission control module failing, is oxygen sensor failing, poor fuel economy, loose fuel cap, mass airflow sensor failing, catalytic converter failure, ignition coil issues, spark plug failure, issues with aftermarket alarm, bad spark plug wires, and a vacuum leak.
2. Erratic Shifting
Erratic or unpredictable shifting is something you need to watch out for along with the check engine light. This means there is something wrong with your vehicle’s transmission control module. The bad transmission control module can result in unintended and incorrect shifting since a vehicle’s automatic transmission relies solely on the transmission control module.
You may need to visit an auto body shop or a mechanic unless your car has a manual override option. This will be necessary to replace or repair the transmission control module before it can hurt the engine.
3. Trouble with Higher Gears
Your transmission should seamlessly shift into higher gears quickly and efficiently when you gradually increase your car’s speed. This is important to accelerate and drive your car on uphill roads. You will notice that the RPM of your car’s engine keeps increasing instead of subtly changing while making the upshift.
Rank #2
- [All System Diagnostics, Professional-Level Scanner] - BLCKTEC 460T is the ultimate OBD2 diagnostic tool for home mechanics and professionals. It supports all 10 OBD2 modes, reads and clears Engine/Transmission/ABS/SRS codes, performs All-System Diagnostics, offers workshop reset tools, and provides real-time live data. It helps you pinpoint issues, assess your car's condition, and prepare for SMOG checks with ease. NOTE: Function availability depends on your vehicle. Before you buy, be sure to use the Compatibility Checker on BLCKTEC website or contact our customer support to verify that the features you need are supported for your vehicle’s specific year, make, and model.
- [12+ Most Popular Reset Functions] - BLCKTEC 460T OBD2 scanner offers 12+ dealer-level service functions, including Oil Maintenance Reset, ABS Bleeding, EPB Reset, SAS(Steering Angle Sensor) Recalibration, DPF(Diesel Particulate Filter) Reset, Throttle Body Relearn, Battery Reset/Initialization, TPMS Relearn, Transmission Reset, Fluid Change Reset, Maintenance Reset and more, enabling you to perform workshop services like a pro. NOTE: Function availability depends on your vehicle. Be sure to use the Compatibility Checker on BLCKTEC website to verify that the features you need are supported for your vehicle.
- [Real-Time OBD2 and OEM Live Data, Freeze Frame Data] - BLCKTEC 460T helps diagnose vehicle issues when warning lights like Check Engine Light or ABS/SRS Light appear. It offers detailed DTC info, ECU Freeze Frame Data, and real-time OBD2 and advanced OEM live data, including Engine, Transmission, ABS, SRS, and more, making it easy to diagnose and resolve vehicle problems. You can view, graph, record, replay, and overlay up to four live data streams in a single graph for better analysis.
- [AutoVIN, AutoReLink, AutoScan, 3X Faster] - Equipped with AutoVIN technology, 460T automatically retrieves the VIN to save you time. Its AutoScan and AutoReLink features scan all of the vehicle's ECUs and detect any fault codes immediately after you plug the scanner into the vehicle's OBD2 port - no button presses required. Additionally, it regathers DTC and I/M readiness information every 30 seconds, simplifying monitor tests. 460T's advanced technology makes it 3X faster than other products.
- [Get RepairSolutions2, the #1 Auto Repair App for Free] - When paired with RepairSolutions2(RS2) App, 460T becomes even more powerful. RS2's Verified Fix Database built by master technicians, provides the parts needed for the repair. Additionally, RS2 gives you access to OEM warranty info, maintenance schedules, TSB, and dealership recall info, making car care easier than ever. RS2 is free with no subscription fees and it stores your car scan reports in the cloud, allowing you to access, share, or print them anytime and anywhere.
Each gear has a maximum speed within that particular spot. You may be unable to reach the necessary speed in such a case. This can be problematic in certain situations. For instance, if you are driving uphill, you need rapid acceleration to move the car forward. Likewise, on the freeway, you need to be driving at a particular speed to be safe and fast.
4. Issues with Downshifting Gears
Problems with the transmission control module are not limited to upshifts and higher gears. Issues can occur when you are trying to downshift as well. Your vehicle can fail into shifting into a lower gear when you want to pass a slow-moving vehicle and hit the pedal to the floor. The car will try to accelerate without actually accelerating rapidly.
The same problem can occur on uphill roads as well. Your transmission needs to be at a lower speed when you are cruising at high speeds and want to slow down. For instance, the automatic transmission should automatically come to the first gear when your car comes to a complete stop.
Recommended Free Tools
A bad transmission control module will not allow your car to stop. It will remain in high gear. This is one of the easiest ways to tell that there is something wrong with your transmission control module. Your car will remain in high gear and won’t stop when you try slowing down.
Rank #3
- 【Full Systems Automotive Diagnostic】 More than checking engine, ABS and SRS, OBDMATE OM970 obd2 scanner performs comprehensive diagnostics on all electric modules. It quickly scans and clears fault codes, turns off warning lights, reads live data, and features Auto-VIN technology.
- 【Live Datastream&4-in-1 Graph】 Easily view live sensor data such as RPM, fuel trims, ATF temperature, wheel speed sensor, battery voltage and so on. OM970 scan tool also supports 4-in-1 trend graphing. Spend just 3 minutes to check – and you'll know exactly what's going wrong, helping you avoid hundreds in dealership diagnostic fees.
- 【One-Click I/M Readiness&Full OBD2 Functions】 Press F1 to get an intuitive corloured form about whether your vehicle's emissions-related systems are operating properly. Help you get smog-check ready quickly. OM970 obd2 diagnostic tool supports all essential OBD2 functions you need. Plus, it features battery voltage test and DLC 16-PIN test.
- 【Straightforward Menus with Easy Navigation】 All functions are easy to understand without obscure decriptions. 3.5" Large screen delivers clear readings while keeping one-hand operation. The car diagnostic tool comes with a silicone protective case and a hard-shell carrying case, ensuring long-lived durability and drop resistance.
- 【Budget-Friendly, No Subscriptions, Free Software Updates】 Plug and play: no bluetooth pairing, monthly fees, Wi-Fi connection, or any other troublesome initial settings. OM970 obd2 scanner works out of the box with the latest software. Lifetime free upgrade.
5. Unable to Change Gears
Your transmission control module is probably beyond repair if the gears are stuck in a particular spot. Usually, the gear doesn’t move forward from the first one in such a situation. The gear can be stuck in neutral as well. This means the transmission will not be upshifting or downshifting, and your car will essentially not move from its spot.
6. Slow Shifting
The transmission control module needs to cycle through several gears at once to be able to change the speeds and gears of your vehicle. This cycle is not as quick or efficient when you have a bad transmission control module. It causes the gears to move too slowly, which can cause poor engine performance and acceleration. Your engine will work at suboptimal capacity, which will eventually take a toll on other parts and components.
Shifting performance may get worse when you are approaching a hill or trying to pull heavy loads. This is another way of knowing that the transmission control module is no longer working the way it is supposed to.
7. Inadequate Fuel Efficiency
Poor fuel mileage and poor fuel economy are common signs of a failing or broken transmission system. Generally, the transmission control module is responsible for poor fuel economy. Automatic transmission engines are designed for smooth and quick gear selection and timing. These are required to provide the most efficient gas mileage and the best possible fuel economy.
Rank #4
- FREE LIFETIME SOFTWARE UPDATES – NO SUBSCRIPTION FEES: Buy the TOPDON AD600S once and keep it updated for years with free lifetime software updates via Wi-Fi—no recurring update fees or annual software subscription costs. Stay current with expanded vehicle coverage and software improvements. A smart-value OBD2 scanner diagnostic tool for DIYers, home mechanics, and technicians. *Wi-Fi is required for initial setup. after setup, most basic diagnostics can be used offline
- 4-SYSTEM DIAGNOSTICS FOR ENGINE, ABS, TRANSMISSION And SRS: Go beyond a basic code reader. The AD600S automotive diagnostic scanner provides enhanced diagnostics for four critical vehicle systems—Engine, ABS, Transmission and SRS. Read and clear trouble codes, view ECU information and live data, and use all 10 OBD2 test modes to troubleshoot check-engine and emissions-related issues with greater confidence. Function availability varies by vehicle year, make, model, and system
- 9 ESSENTIAL SERVICE FUNCTIONS FOR EVERYDAY MAINTENANCE: Handle more maintenance jobs at home or in the shop with 9 frequently used service functions: Oil Reset, Brake/EPB Reset, BMS Reset, SAS Reset, DPF Regeneration, TPMS Reset, Throttle/ETS Relearn, ABS Bleeding, and Injector Coding. From brake service and battery replacement to steering-angle calibration and injector-related maintenance, AD600S helps reduce unnecessary trips to the repair shop
- 90+ VEHICLE BRANDS, CAN-FD & FCA GATEWAY ACCESS: Designed for broad vehicle coverage, the TOPDON AD600S works with 90+ vehicle brands and many OBDII-compliant cars, SUVs, pickups, minivans, and 12V light-duty vehicles from 1996 onward. Support for CAN-FD and FCA AutoAuth gateway access helps extend compatibility with newer vehicles. Vehicle and function coverage varies, so please provide your VIN before purchase if you need to confirm a specific diagnostic or service function
- EASY 5-INCH TOUCHSCREEN, AUTOVIN & 4-IN-1 LIVE DATA: Diagnose faster with a responsive 5-inch touchscreen, Android 11, 32GB storage, AutoVIN vehicle identification, built-in DTC lookup, and live-data viewing in text or a 4-in-1 merged waveform graph. Save, share, print, or email diagnostic reports for easier troubleshooting and record keeping. AutoVIN and individual diagnostic functions are vehicle-dependent
Your engine and timing can get affected if you have a transmission control module that is damaged or has gone bad. The engine will have to work harder than usual and will overheat. At the same time, there will be no improvement in performance. This can cause the engine to utilize more fuel than necessary. It is not just expensive on your pockets with frequent tank fills, but also bad for the vehicle.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Replacement and Repair Costs
It costs anywhere between $500 and $900 to replace a transmission control module. Parts for the transmission control module cost from $450 to $700. You should expect to pay labor costs to up to $200. In fact, you should ask your mechanic what their hourly labor rates are by ordering a new TCM online.
A significant portion of the cost is geared at the expense of parts. Replacement and repair costs can vary greatly depending on the car’s make and model as well. Don’t forget to take account of taxes and fees that will get added to the overall cost.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Repairing a transmission control module can be a stellar option and also thrifty in the short term. Generally, repairs are at least a third of the cost of replacement. You should expect to pay somewhere around $300 on average to repair a regular TCM. However, it would be best if you got it repaired by solid and trained mechanics. It can be risky if the TCM is not repaired right. Make sure you have it repaired by someone offering a warranty of sorts.
Best Value
- [Brand-New ArtiDiag500] We've got everything you're looking for! Forget basic OBD2 scanners; TOPDON's ArtiDiag500 car scanner offers more. The all-new ArtiDiag500 not only includes full OBD2 functions and 4-system diagnostics but also provides DIYers with 6 maintenance services. The brand-new, cost effective AD500 is back in full swing!
- [4-System Diagnostics] DIY enthusiasts, take notice! Will these 4-system diagnostics be the treasure you've been seeking? The ArtiDiag500 code reader offers in-depth testing for the engine, transmission, ABS, and SRS systems, reading fault codes and data streams. It also visualizes real-time data in chart form, simplifying complex data for storage and future playback, aiding DIY users in problem detection.
- [6 Reset Functions] Hey, hang tight for a moment. With these 6 reset functions, the ArtiDiag500 has got you covered. It offers throttle adaptation along with reset capabilities for Oil, SAS, TPMS, BMS, and EPB. Seamlessly aligning the throttle, battery, tires, and brake pads with your vehicle, it also adjusts the steering angle and turns off the oil light. Looking to restore your car to its original condition? Look no further than the ArtiDiag500.
- [Multiple Functions] The Smart AutoVIN of this TOPDON OBD2 scanner keeps track of your manual selections for vehicle make, model, and year and directs you to the suitable diagnostics. Max 4 Live Data streams integrated for much easier data processing. Diagnostic feedback online with this diagnostic tool to help you get tough repair operations well-completed. Real-time car battery voltage monitoring identifies probable vehicle defects.
- [Wide Vehicle Coverage] ArtiDiag500 currently supports 67+ car brands, 10,000+ models, covering most vehicles worldwide. Supports cutting-edge CAN FD protocols, making it compatible with modern vehicles including 2020+ GM & Chrysler. It supports FCA AutoAuth (official Secure Gateway access) to stay up to date with newer models from Chrysler, Jeep, Fiat, and others. Plus, it's fully compatible with Android 11 for smoother use.
Also, it may be possible that your local mechanic is unable to repair the TCM properly. They may have to ship it to a non-local location. This could take longer. If you cannot do without your wheels, you should seriously consider getting a replacement instead of wasting time and money on repairs.
Driving with a Faulty TCM
Many people get tempted to drive with a faulty or bad transmission control module after determining the prices. Your car may not be drivable if the transmission control module becomes damaged or fails. The car may get disabled or only have 1 – 2 functioning gears. The car may not deliver the same level of performance as required to drive safely.
The more modern vehicles can enter into “limp mode.” This is when the vehicle identifies as having a bad transmission control module and stops being drivable. The TCM in such a case would require replacing or repairing. Limp mode is an inbuilt security feature in most vehicles. In this case, the car’s computer activates the transmission control unit or the engine to pick up on the car’s fault.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Once the transmission control unit picks up the fault, the limp mode causes certain non-core components to switch off. This can be unimportant things, like electronics and air conditioning. But, the limp mode can also cause the car to go slower. This mode is a direct sign of a faulty TCM. Sometimes, limp mode and check engine light occur simultaneously.
This is usually when there is a problem with the transmission wiring. Low performance and under boost are few other symptoms of limp mode. These are again related to faulty engine sensors and defective engine components. These two signs are usually because of faulty brake system wiring or engine wiring.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
