Can't replace TCM on 2016 Mazda6 without replacing entire transmission?

[LarryLondon]

2016 Mazda 6 GT
90,000 miles
2nd owner (so powertrain warranty expired 7 months from in-service date, earlier this year)

I've kept the car in great shape.

The last few days, it has been experiencing transmission delays. Mostly when the engine is cold, when I shift from P to D, it does not engage for about 5 seconds, I then feel two short "shudders", and the drive is then engaged and the transmission operates flawlessly from that point on. Car drives great.

Had it at the Mazda dealer today. They were able to recreate the issue right away. They did a thorough checkup and found absolutely no issues.

No fault codes. Transmission checked out good, fluid good, levels good. No other issues. It was in the shop for a couple hours.

The tech surmised that it would most likely be a Transmission Control Module fault, even though it's not reading any faults. They checked for TCM updates but none were available.

They said it was OK to keep driving it since there were no issues discovered. However, they said if it's the TCM, it cannot be replaced without replacing the entire transmission.

No idea what to expect from this point, I feel like my car is broken even though it's in great shape otherwise.

Any ideas? Is this problem likely to get worse?

If I decide to get rid of the car, how much will this affect the trade-in value?

Thanks in advance.

 

[Silly Wabbit]

Some good info below. Maybe your dealership is trying to say you can't purchase the tcm separately so the entire assembly needs to be replaced. Try calling different parts department and see if they can find you the part # for the tcm.

Mazda Transmission Control Module Buyer's Guide | REALMazdaParts Blog | RealMazdaParts.com

Without A Transmission Control Module, Your Automatic Transmission Can't Function. This Buyer's Guide Answers The Most Common TCM Questions.

www.realmazdaparts.com

Reddit - Dive into anything

reddit.com

 

[LarryLondon]

Excellent info, thanks.

Interesting quote from the bottom of that page: "Replacing a TCM is easier than it sounds. It doesn't require any advanced automotive knowledge. It's not nearly as complicated or time-consuming as replacing an entire transmission."

I'm assuming that probably applies to older models and not mine.

Notes from the dealership said "The TCU is an internal component to transmission and can only be repaired by full transmission replacement."

Interesting that they referred to it as "TCU" which I am assuming is just a misprint, because the service rep definitely referred to "Transmission Control" unit or module.

 

[LarryLondon]

BTW, I also saw another thread on this site where a user noted a similar issue, and said they drained/refilled the transmission fluid and the problem went away. Wondering if that might be worth a try.

 

[Lazy2.5]

unable to replace the TCM without changing the entire transmission is a complete load of nonsense.

I would suggest taking your car to a reputable transmission shop and see what they have to say. The car is likely long overdue for a transmission filter and fluid change, which I am sure will dramatically help.

otherwise, if the TCM is not throwing any codes, there's nothing wrong with it.

 

[LarryLondon]

So...I decided to call another Mazda dealership, and here's what I was told. On older vehicles, the TCM was on top of the engine and much easier to replace. On the 2016 it sits inside the transmission, making it more complicated. However, they said it CAN be replaced without replacing the entire transmission. They gave me an estimate of $2,500 for the repair. Still a big bite, but way better than replacing a transmission.

I'll be having a "conversation" with the manager at the other shop that told me the wrong info. I don't think I'll be taking my car there again unless he can give me a good explanation.

I'll try the fluid change and see if it helps. No plans to replace the TCM unless it starts throwing codes. But it's a load off my mind knowing that I'm unlikely to need a full transmission replacement.

 

[Lazy2.5]

So...I decided to call another Mazda dealership, and here's what I was told. On older vehicles, the TCM was on top of the engine and much easier to replace. On the 2016 it sits inside the transmission, making it more complicated. However, they said it CAN be replaced without replacing the entire transmission. They gave me an estimate of $2,500 for the repair. Still a big bite, but way better than replacing a transmission. I'll be having a "conversation" with the manager at the other shop that told me the wrong info. I don't think I'll be taking my car there again unless he can give me a good explanation. I'll try the fluid change and see if it helps. No plans to replace the TCM unless it starts throwing codes. But it's a load off my mind knowing that I'm unlikely to need a full transmission replacement.

The explanation involves their interest in maximizing profit at your expense, that's it.

Don't change just the fluid, make sure the filter is changed as well.

 

[Silly Wabbit]

Looked at the service manual and the tcm is built into the valve body...

2016 Mazda 6 Grand Touring Sedan 2.5L SKYACTIV SULEV Automatic Transmission Valve Body. CX-3 - FZ2121100J | Jim Ellis Mazda Parts, Marietta GA

Automatic Transmission Valve Body. CX-3. CX-5. CX-5; 2.5L; w/o Turbo. 2016 Mazda 6 Grand Touring Sedan 2.5L SKYACTIV SULEV. Genuine Mazda Part - FZ2121100J. Ships from Jim Ellis Mazda Parts, Marietta GA

www.jimellismazdaparts.com

Take Snorting's advice and change the filter + renew fluid first.

 

[LarryLondon]

Awesome, thank you so much.

I'll get the fluid/filter service done in the next couple weeks.

 

[Lazy2.5]

Awesome, thank you so much.

I'll get the fluid/filter service done in the next couple weeks.

as i've mentioned before, a good transmission shop will be able to help you out here.

FWIW, my 2015 6 has over 301,000KM on it. the trans filter and fluid has been changed 4x already. it's had a drain and fill once early on in it's life. The transmission shifts very well. absolutely no jerking or hesitation going into drive.

 

[LarryLondon]

Update--

I went to a highly reputable transmission shop yesterday and had the fluid and filter replaced.

The transmission "guru" there said that delays are somewhat common on Mazdas and advised against doing anything crazy like spending a few thousand dollars unless it really started to go bad. I concurred.

They did the service and said the pan looked good and everything was fine.

At any rate, after the service it is still exhibiting the same delays so far. I'm still glad I had the service though, at 90,000 miles. What's also weird is that earlier this week, one day it barely did it at all.

Other than that quirk, the car is performing great, so I'll just continue to roll with it and monitor. My only concern is that whenever I trade or sell the car, it will lower the value of the car because anyone who drives it will notice the quirk. I certainly wouldn't buy a car that was doing that.

 

[Lazy2.5]

Update--

I went to a highly reputable transmission shop yesterday and had the fluid and filter replaced.

The transmission "guru" there said that delays are somewhat common on Mazdas and advised against doing anything crazy like spending a few thousand dollars unless it really started to go bad. I concurred.

They did the service and said the pan looked good and everything was fine.

At any rate, after the service it is still exhibiting the same delays so far. I'm still glad I had the service though, at 90,000 miles. What's also weird is that earlier this week, one day it barely did it at all.

Other than that quirk, the car is performing great, so I'll just continue to roll with it and monitor. My only concern is that whenever I trade or sell the car, it will lower the value of the car because anyone who drives it will notice the quirk. I certainly wouldn't buy a car that was doing that.

personally I would not just keep driving with a hesitation into drive like that.

 

[sinistriel@]

A hesitation going into drive longer than about a second or two is indicative of a pressure problem inside the transmission. This can be caused by multiple issues. Some of the concerns that can cause the delay are pump wear, this is not likely due to how the pumps are built in the Skyactiv, if this were the case you would need to have an overhaul as it would burn the clutches very quickly and all your shifts would be bad. Fluid level not being correct can also cause this but if it was just filled and they did it correctly this should not be a concern.


Next, it could be a solenoid issue but is not likely. To make 1st gear there are two solenoids in play. Solenoid 4 is sending line pressure to the Low/Reverse clutch set, this operates in P,R,N and stays on for D, so we can eliminate this solenoid as a cause. Solenoid 1 turns on and sends pressure to the Low Clutch which operates until it turns off for 5th. It could be slow to respond but that would cause a bind when shifting into 5th. An issue that we are starting to see in the earlier cars is Low/Reverse accumulator wear. We are seeing this cause delayed engagement and eventually damages the one-way clutch that the Low/Reverse clutch set rides against and has uneven apply pressure on. This causes pressure to bypass the accumulator and take time to charge the circuit.

Mazda only sells the TCM and valve body as one unit and it needs to be programmed. Most dealers from most OEMs will not open a transmission up to find the issue because they are not trained on what to look for and it can be a very time consuming process. They could try a valvebody/TCM combo but that may not be the issue and you've spent a few thousand only to need a transmission replacement because they don't do internal repairs at the dealership. First pics are the valve body and then the TCM on top, 3rd and 4th pic is the Low/Reverse accumulator wear and the 5th is the repair, you bore the hole bigger and replace with a larger anodized valve.

The video is a link to a CX-5 we recently built that had no transmission codes but had a failed one-way clutch. There were no codes for the transmission, just because they told you there are no codes does not mean there is not a problem, they just may not know how to properly diagnose the situation. I would keep an eye on it and monitor if it worsens. 2017 CX-5 broken transmission

 

[Lazy2.5]

I'm willing to bet it's the valve body. I suggest getting the opinion of one more transmission shop. If they also say to let it be , well.. then. Do that.

 

[LarryLondon]

Thank you so much for sharing all that knowledge.

To reiterate--this started abruptly just about 4 weeks ago. It has basically been the same since then, no changes:

This basically ONLY happens in the morning when the engine is completely cold. I start the car, wait about 30 seconds. Then, with my foot on the brake, I shift from P to D. The dashboard indicator shows D immediately, and shift lever moves smoothly. I keep my foot on the brake for about 3-4 seconds and wait to feel a little "bump". Sometimes the bump can be very faint, randomly sometimes it can be a bit more pronounced. When it's more pronounced there are definitely TWO distinct "bumps" very close together. "Buh-bump". Sometimes I barely feel the bump, but it's there.

As soon as I feel the bump the car is good to go and operates normally from that point on for the rest of the day. If I leave the car parked for more than about 4 hours, it MAY do the same thing. But for the most part it shifts from P to D normally until the next morning. Regardless, whenever I shift the lever to D, I always keep my foot on the brake for 3-4 seconds waiting for the bump. Then I go about my business.

Shifting to R, absolutely no delay and no problem ever.

The transmission specialist I took it to said this type of thing is not uncommon on Mazda transmissions. Is that true? He's not the only one that has said that.

It seems like there's not much I can really do except wait and see if anything else happens. Without a firm root cause, there's not a repair that would be worth trying.

I did have one guy from my office who has a lot of knowledge suggest it could be a worn rear differential bolt. Don't know about that.

I appreciate the knowledge. I'm not a mechanic in any sense and don't work on my car at all, but rely on professionals. Just casting about for some root cause analysis.

 

[sinistriel@]

I would verify transmisison fluid level to make sure it is betwen the two marks on the dipstick at the correct temperature with the vehicle running. If the fluid level is correct and it happens on a cold start or when it's cooled down it is very likely valve body wear and as the metal warms and expands it seals better. This is very common across multiple transmission families.

I would call into question any transmission expert that believes a forward engagement of 3-4 seconds is normal, it's not. For reference the factory spec for the Skyactiv is .4-.7 seconds from neutral to drive.

When putting the car into reverse the transmission commands much higher line pressure vs a forward engagement and it's not uncommon again across multiple transmission families that are experiencing wear to have a normal reverse engagement vs delayed forward.

I made a video awhile ago about how to put the transmission in learning mode. This will force the transmission to start over with new values, this may effect a change for you, it may not.

Mazda Skyactiv AT initial learning mode. #skyactiv #mazda #automatictransmission

This is a quick video to show how to put a Mazda Skyactiv transmission into initialization mode. This clears all the shift adapts and learned clutch values. ...

youtu.be

 

[LarryLondon]

To be fair to the transmission guy, he didn't say it was "normal", just that it was not uncommon. It's clearly not normal for my car!

Great video, I will give this a try in the next couple days. Thanks again.

 

[Lazy2.5]

I understand that it is quite a bit of work to assess, understand, let alone fix an issue like this, but I totally agree that at least one more opinion regarding your AT would be helpful here. At the very least, if you notice that it is getting worse, or that the worn valve body start to affect actual shifting, you'll need to address this.

Essentially, something is causing a delay from P to D, the AT acknowledges this, hence that abrupt "forced" shift into drive. that's the rough explanation I got from a buddy who worked at a tranny shop years ago.

 

[LarryLondon]

I really appreciate the responses and people taking time to really work through this with me.

The problem is, I don't see any potential fix that isn't going to be in the thousands of dollars. Worn valve body? Makes sense, especially since I drive in a LOT of heavy stop and go, speed up/slow down traffic and as such that tranny gets a massive workout on a daily basis.

But how to be sure that's the issue? I can't spend a couple thousand bucks thinking that it "could be" or is "probably" the issue, then to find out it isn't and the only way to fix it is replacing the whole transmission. Now you're talking about just bleeding money.

It seems like the only way to really find the root cause may be to open up the transmission, and I don't know if anyone wants to do that or how much it would cost.

I'll see if there is another good transmission shop and consider taking it in for one more opinion. But I feel like I've covered all the bases pretty well at this point and understand what my options are. At this point I'm not really too stressed about it.

 

[ChrisMazdaG]

Unsure if you've moved forward or not but I will also say that the tcm is indeed built into the valve body and the valve body is likely the issue. I have a 2016 Mazda 6 and the tcm is on the fritz. It will throw at, parking brake, engine, traction control lights randomly, go into limp mode randomly, and have the start button flash red and refuse to start occasionally. Every code, from engine light to the abs code is all tcm failure or lost communication with tcm. And it is an entire valve body and tcm assembly that needs replaced. I've reset the transmission, I've unhooked the battery, ECT. It'll drive fine for a week then freak out again. I even replaced abs sensors in case they were reading improperly and confusing the computer. My Mazda dealer says they've never replaced a valve body or tcm in these cars but can do it. Aamco says they can do it as well. The issue is it will need programmed to the vehicle it is installed in. They are vin locked. It can be replaced without replacing the entire transmission. I attached photos of the codes I have, if you don't have similar codes I don't think it'd be your tcm necessary. .