Mazda 3 Dodgy Transmission Control Module, Affordable Repair

My 2010 Mazda 3 was having some minor troubles with gear changes and after running my OB2 scanner I found that it was showing numerous transmission faults. it turns out that Mazda in their infinite wisdom decided to mount the TCM ( Transmission Control Module) right on top of the hot gearbox and directly under the battery box. This over times causes the TCM to get overheated and fail. There are companies rebuilding the TCM control boxes but the cost of repair is extremely expensive, so I opted for a second hand module, and promptly relocated it so it cant happen again.

[@buddymartin7923]

Changed my daughter's twice. (Had it repaired and preprogrammed) and BOTH had a brown/black spot burned into the epoxy that fills the case. I used spacers and longer bolts to get some air gap but your fix is better.

[@BruceFurlong-GagaCulture]

I should have dismantled mine to have a look what goes wrong. I don't have the car anymore as i bought another car since then. I did have a CX7 for a while, and they are another piece of Mazda ingenuity with multiple issues and should not exist including, turbo oil feed hoses that are undersized, and worst of all a faulty EGR system that caused the car to randomly smoke under certain situations. Overall though i have to say i quite like the cars, you just have to know how to repair them when it all goes wrong.

[@Uno-he9rm]

This is the smartest TCM relocation I’ve seen. Big up man👊

[@AMicheals]

Had mine repaired by a tech who specialises in them for $300 here in VIC 7 years ago. Car has done an additional 120,000km since repair and still going strong. Solder fails and cracks due to vibration and heat.

[@aspenridge6043]

Whereabouts in VIC?

[@SteveInQLD007]

Love the idea and it makes more sense to have it where it has a chance of getting some cooling. Did you run an earth lead from the TCM to the chassis or is the bracket earthed anywhere?

[@chloeleedow7250]

Looks good mate will definitely do mine before it dies, not sure how it hasn't already on bk mazda 3 2008 with 225,000ks lol nice neat Job 💪

[@Nemspy]

I have this issue with my 2009 and Mazda are absolutely adamant that these are “locked to the car” and a second hand one will not work. Even the nice guy who I chatted with off the record and phoned a friend who was an “expert” he it “confirmed” that it wasn’t possible.

[@BruceFurlong-GagaCulture]

He is simply wrong, I am not the only person to have done this successfully. I spent a lot of time doing the research before making the change and it worked perfectly. You have to know the series of the TCM and buy one from the same series as i speak about in the video. Its not even important to get it reprogrammed as the unit learns the shift position anyway over time. Mazda created the issue by having such a useless location for the TCM. Mazda make a fortune selling these units as they aren't cheap and the installation and programming is on top of the cost of the unit for an issue that really should not exist.

[@FlipBoji]

It’s crazy I think I’m having a tcm issue because my at light is active, however, my engine code is giving a p0720, which I’ve replaced and it went away for a few weeks, but it came back with the at light

[@SilverforceX]

Same thing happened to wife's 2012 Mazda 3. So lame that they put that module right between those two heat-traps, combined with Australia hot summers, no wonder they go dead so fast. These units are so expensive on the used market too, and refurbished ones are like $1,000! Mazda dealer wanted to charge $2,000 for a new one!

[@Bitgisa]

Hi, can I ask where you purchased the replacement TCM from? do you recommend the brand new one or do you think refurbished ones are okay? thank you so much if you reply to this comment

[@BruceFurlong-GagaCulture]

Sorry it was a second hard parts place on the south side of Brisbane. Its more than a year since i got it and i don't remember the name of the place. I rang around a lot for the best deal on one.

[@haitipapperi2932]

My 2010 says shift solenoid E stuck on do I have to change the solenoid Other things it says lost communication with the tcm I don’t know what to do

[@tunghon2230]

I having problem with SP25 2009 P0720 code. I swapped out VSS sensor with new one and it still randomly cause P0720 code wonder if my TCM is cooked.

[@benjamin3455]

thank you my mazda 5 2008 has a similar issue i am hoping its not the TCM praying . will carry out a diagnosis thank you

[@SilverforceX]

If you're in a hot region of the world and Mazda 3 transmission problems, it's 99% likely TCM.

[@jameswaugh183]

That last bolt under the engine counter weight was a fricking nightmare haha

[@BruceFurlong-GagaCulture]

yeah I do remember that one was hard to get to. Lucky on mine it wasn't very tight and I had a few tools to get it undone. Once its moved to the new location those issues go away though and its really easy to remove and sort if it ever fails again.

[@dylancolville8555]

Was your AT light coming on all the time or just on for a minute then off again?

[@BruceFurlong-GagaCulture]

It was randomly coming on and off. Its risky when it does that, as it can change gear into the wrong gear and destroy the gearbox.

[@Karen-ur6mm]

How long did that tcm work after relocating it there? I put mine in the lines like they said and it worked for a year and is out again

[@BruceFurlong-GagaCulture]

Mines still running with no issues, since i made this video.

[@chloeleedow7250]

Probably a lot of vibrations bro this mans job wouldn't vibrate at all really, vibration is killer for solder, dry joints etc probably an easy fix for a sparky with a reflow solder station because I doubt it's fried from heat again if it's new since.

[@dylan6996]

for the tcm if I buy a used one from a car in a junkyard or something do I need it reprogrammed to my car or I just grab it connect it and good to go

[@Uno-he9rm]

No need to reprogram it but please be aware that the part numbers should match except for the letter at the end. The letter is just there to inform on whether the part is updated or not… e.g A being the first one installed during initial assembly and B being an upgraded part made overtime. In addition The number or letter in bold above the part number should be the same as the one on the TCM coming from your car.

[@BruceFurlong-GagaCulture]

@@Uno-he9rm perfect explanation

[@dylan6996]

@@Uno-he9rm I tried 2 both had the same everything under the big E on the module but the code under that one of them was the same the other had a 2 instead of a 4 so I went for the one that matched how would I have known if it wasn't a match though if I would have tested anyways the one with the different number

[@Uno-he9rm]

@@dylan6996 from what I heard from the mechanic who helped with my car is that, it would work for some time before throwing the same error code and giving out the same problem as a damaged TCM. He even said on some occasions it could take less than an hour for it to start doing so.

[@dylan6996]

@@Uno-he9rm Thanks for the info, I think I might need to go back to that place and check if the codes match I know the big bold letter was E on all if them and the part number under that big letter was also the same on the 3 TCM (BOLD LF8M 18 9E1F and big letter E on top) but under those 2 theres other numbers and letters not in BOLD that I'm not sure matched the last number I'm not sure if it matched I think on that writing the one I had was written 2 and when I checked my new one it was 4 the last number its not the part number so I don't know if its significant but might as well double check. So far though the TCM has been working fine for the 2 days or so ive had it.