7 Symptoms of a Bad Transmission Control Module (and Replacement Cost)

The transmission control module (TCM) is a vital component of any vehicle with an automatic transmission system. Rather than relying on hydraulic or mechanical control over a transmission system, newer vehicles use a transmission control module instead. A car’s TCM will likely never need replacing, but if you have a bad transmission control module, immediate replacement (or repair) will be necessary.

This module is basically a computer which communicates information to other computer systems within the vehicle. The purpose of the transmission control module is to help the automatic transmission choose the best gear to be in at any given time. That way, the driving performance and fuel economy will be at the optimal level. 

Top 7 Signs of a Bad Transmission Control Module

The transmission control module can often be found below the cover at the back of the transmission case. It should be just below the engine control module’s position. Sometimes it’s found under the center console in the interior or even under the hood near the battery or inner fender panel.

If you ever have a problem with your transmission control module, you’ll need to have it inspected right away. A bad TCM will spell trouble for your vehicle and your ability to drive it. Fortunately, there are a few basic symptoms that you’ll most likely notice before this happens.

#1 – Check Engine Light

bad-tcm-symptoms

If the Check Engine warning light illuminates on your dashboard, it could mean several things. But if you notice any problems with your shifting in addition to the Check Engine light being on, then it is most likely a problem with your transmission control module or some other component of your transmission system.

In any event, get your vehicle checked out immediately by a mechanic or use your own scan tool to check for any Diagnostic Trouble Codes (DTC). If code P0700 shows up, you likely have a problem with your transmission control module.

#2 – Unpredictable Shifting

Since an automatic transmission system relies on the transmission control module to do the shifting, a bad transmission module will cause incorrect or unintended shifting. This can prove to be anything from an annoyance to causing a serious accident.

For instance, if your car shifts to neutral or any other gear that it normally wouldn’t shift into without warning, then your control module will likely need to be replaced. Otherwise, it will be very dangerous to continue driving. Unless you have a manual override option in your vehicle (example: paddle shifters), you will need to get your car towed to a mechanic and have the module replaced.

#3 – Problems Shifting Into Higher Gears

As you gradually increase speed, your transmission should correctly shift into higher gears at the correct time. When this doesn’t happen, you’ll notice that your engine’s RPM simply keeps increasing instead of slightly dropping an upshift occurs.

Because each gear has a maximum speed it can go to, you may never reach your intended speed if the faulty TCM refuses to shift to a higher gear.

#4 – Problems Downshifting

This is similar as above but in reverse order. If you’re cruising down the freeway and take an off-ramp, your transmission should gradually be going into lower gears as your speed decreases. At a stop, an automatic transmission should be in first gear so it’s ready to go when you need to start moving again.

If your transmission control module is bad, you may still be in a high gear as you’re coming to a stop. When it’s time to start moving again, you’re in a too high a gear for proper acceleration which may even prevent you from moving at all.

#5 – Stuck in the Same Gear

This usually presents itself as being either stuck in neutral or first gear. The transmission simply will not shift and you either won’t be going anywhere (stuck in neutral) or you’ll be limited by the maximum speed of first gear.

#6 – Delayed Shifting

The speed of your vehicle relies on cycling to various gears at the appropriate timing. If you have a bad transmission control module, then it will cycle to next gear too slowly. This will impact the momentum of your acceleration, causing you to lose speed rather than picking up speed. When you approach a hill, the shifting performance will be even worse.

Worst case is when you’re attempting to pass a slower vehicle on a 2-lane road and your vehicle refuses to downshift immediately so you have more torque available to make a quick pass.

#7 – Poor Fuel Economy

Problems with your transmission system usually result in bad fuel economy. An automatic transmission is designed for optimal gear selection and timing to provide you with the best possible fuel economy.

If you have a transmission control module that’s bad and affects this timing, then your engine will end up working harder than usual. This means it will consume more fuel than usual, causing you to spend more money at the gas pump.

Replacement Cost

transmission control module replacement cost

The replacement cost of a transmission control module will be anywhere from $500 to $900. You can expect the parts costs to be around $450 to $700 while the labor costs will be around $50 to $200.

Of course, you can order a new TCM online and ask a mechanic what their hourly labor rates are. However, most of the cost for this replacement job goes toward the parts cost itself and it can vary greatly by car manufacturer. You can expect taxes and fees to be added to the total cost as well.

Repair Cost

Another option is to repair your TCM. The transmission control module repair cost will in almost all cases be lower than replacing with a new module. On average, expect to pay around $300 to repair your transmission control module. While most TCM repair businesses will offer a warranty of some sort, it does pose a bit more risk if the repair is not done right.

Also, you may need to ship your bad TCM to a non-local location so if you can’t afford not having your vehicle for a few days, replacement would be the fastest method.

 

Comments

    • Just like any other computer, failure of the TCM is often due to an electrical issue (such as a voltage overload), water (corrosion builds up and eventually causes a short circuit), or damage due to too much vibration or stress.

  1. Will a bad transmission control module cause irregular motor revs as well as confusing shifting,

    Let me explain a bit further

    i own a 2003 Dodge Durango 4.7 AWD with 4×4
    last week i was driving down the highway in town, traffic started to slow and the durango went from just coasting at about 70 km/h with about 1000 rpm and did a really hard and sudden down shift into low range …given the speed i was able to maintain at 5000 rpm i knew it was in 2

    i got off the highway let the truck cool down which did not take long since it was minus 35 c

    i started the truck and then the rpm started waving between 500 rpm and 1500 rpm just randomly, i figured it must be the Throttle Position Sensor, I started to head back to my house to park and about half way there when truck hit normal operating temp it started randomly shifting in and out of low range sometimes putting itself into too high of a gear and would stall out, after getting it home i realized it needed a new alternator and battery, so out i went and replaced those along with the Throttle positioning sensor in the freezing cold, got it running and at first it was doing the same thing with the RPM also the voltage meter on the dash was leaning to the right just a bit off center but according to the voltage tester i was perfect, so i scanned it with OBD2 and it threw a TPS and TCM code, so i took it for a drive knowing the TPS was new and needed to do its thing, had my buddie run a live scan with his machine while we were driving, and both codes cleared themselves, Yesterday in minus 30 c weather it started doing the same thing again only the RPM dont fluctuate as much but transmission goes from like 4th gear for instance and drops to low range and will shift if i hammer it , when it starts the RPM is really high at idle ….1800 to 2100 and will rev on its own in that range until i give it a shot of gas then it levels down to about 800-1100 and once again revs in that range on its own, when the operating temp is cold it will shift like its supposed to , once operating temp is achieved it begins selecting random gears, usually Low range 1 and Low Range 2, if i punch it hard it will shift but not until rpm’s get above 6000 which is insane,

  2. Kindly I need help please. My vehicle is unable to start, is just cranking. We tried to check the all electrical components and they are working. What could be the problem?

    • Unfortunately it could be other things. Bad fuel pump, clogged fuel filter, fuse, and bad crank position sensor come to mind.

  3. 2001 pt cruiser in limp mode diagnosed pcm replaced with new one also transmission solenoid with input and output sensors transmission oil with filter still same need help

  4. Good morning, my 2010 Chevy Tahoe had been having issues getting into first gear with very slow acceleration but RPM into the 2000 range. At first it would take a hard here then after the first gear it’s fine. I was told that was being caused by the motor mount needing to be replaced. Fast forward months later I haven’t fixed the motor mount but now I’m getting the transmission control module or solenoid error. Is the transmission module or maybe the mount replacement

    • Not sure what a bad motor mount would have to do with your first gear issues. I can’t tell if you’ve scanned the ECU for trouble codes but if it was the transmission control module, it would show up there.

  5. I have a 2013 dodge dart areo 1.4l double clutch transmission. The TCMs were recalled but I had no idea of this recall until my transmission started grinding and clanking. Now my transmission is out. Is the tcm to blame for this. And if so. How am to go about getting the dodge dealership to pay for a new transmission in my car?

    • In most cases, the manufacturer is required to fix the issue if it’s related to the recall. Contact the dealership.

  6. I have a 2012 Chevy Cruze. The engine was slipping between gears 2-3 and 3-4. The tachometer would flare, and the engine would race before it shifted into a higher gear. It also had a rough downshift that felt like a jerk or pop of the clutch. It worked best at cold temperatures but had the most problems when it was hotter outside. I took it to a transmission specialist, and they determined that it was the “transmission control module”. They didn’t have to take out the whole transmission to get to it, but it was quite a bit a work and ran upwards of around $1,500 to fix. In the end it was worth it for us, because we weren’t in a position to trade up.

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