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Discussion Starter #1
So I drove to work, drove to lunch and back, everything fine and the car hasn't had a single modification in at least a year. When I go home for the day, I pop it into reverse and the car makes a big clunk.

AT light is on, and there's a CEL code U0101 error communication TCM. The car is at 67K miles and the last time I had an issue was like at 20k miles when it needed a purge solenoid valve. Since this AT problem occurred so spontaneously it makes it harder for me to figure out what went wrong.

Anyways, here's what I tried:

1. Deleted the cel code, it came back instantly.
2. Reset the ECU, delete the code. Code came back instantly.
3. Reset the ECU, start the car in neutral. Code still there, AT light always on.

The second time i put the car in reverse, it made another big clunk so I avoid putting it into reverse now.

I towed the car to a nearby Mazda dealership and there it waits for a $98 diagnostic.

I am out of warranty, the car is a 2006 Mazda3S GT with intake, headers exhaust. I have a scangauge but it's never given me problems so I left it in there in case the mechanic wants to blame it.

If it needs a new PCM, I'm not sure if my non-dealership mechanic will be able to do that or not. I did a search and this only happened to like 2 people and there were no follow up reviews on what needed to be done to resolve it. Thus, I'm posting here so I can follow up with what needs to be done. :)
 

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Discussion Starter #3
Yeah thanks, it's been a while since I posted here on the forums.

Browning Mazda has been supercool so far and are trying to isolate the problem to either the PCM, wiring harness, etc.

In the mean time I can start looking to see if there's a solution out there for PCM related mods for tuning capabilities in case I have to do PCM work and the quote from Browning is too expensive.

Also, I tried calling Mazda Roadside Assistance and my coverage stopped in 09'. However it was $66 to have a flatbed tow truck pickup my car using their 800 number which isn't too bad since it was a 10 mile tow in rush hour. I also got a flatbed just in case because my car is lowered.
 

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Yea, I don't post as much as I used to either, although I still visit the forum daily. The "clunk" sound in reverse has me thinking something other then computer/wiring? Whatever the problem turns out to be, I hope it's not an arm and a leg. My '06 has as many miles as yours, so I'm more then a little interested in this!
 

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Discussion Starter #5
Here's an update.

Browning Mazda didn't find what is wrong so they need to take the TCM out of the car.

This raises the diagnostic and testing fee from $100, to $200. :(

This was earlier today so now I'm thinking they might suggest to have the TCM replaced.

Either way, I'm out $200 just to have the TCM tested which I will pay for because testing the car electronics is sort of out of my comfort zone.
 

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Discussion Starter #6
As I suspected, the TCM failed every test they threw at it, but it did have good power and ground going to it. So apparantly this was just a complete transmission control module failure.

The TCM is $613 for the part to be ordered directly through from Mazda's warehouse in Irvine.

Mazda charges 2.5 hours of labor to install the new TCM and test it. Their labor rate for this is $110.80 per hour.

So the grand total is $890 + 9.75% sales tax for a new TCM installed... They waive the $200 diagnostic fee.

Well... now I just have to wait 4-5 days since the TCM is a special order part.

So I don't bump this thread.... I'll add some info to those that do searches for this sort of problem.

The TCM module died, same problem happened to another PZEV 06 mazda3s that my co-worker has. He paid $1400 at Irvine Mazda since he needed a transmission flush.

My ATX fluid was fine because I'ved did a flush twice in 67k miles and I have an atx cooler.

Anyways the repair bill costed $957 total. $613 for the part + tax and labor.

Browning Mazda did a decent job, and no complaints from them for my mods because I'm a paying customer (not warranty work) so they make more money from these jobs on both parts and labor.

THey replaced the TCM which is located on the transmission itself. My only complaint is they removed the plastic cover under the glove compartment and left it on the floor, and they also didn't give me a car wash but that's no biggy. They also refuse to test drive a car that's not 100% street legal, but I understand that.

The tell tale signs your TCM is dying is your shifts get a little more rough when you downshift, and shift into reverse, etc... If your atx goes into limp mode, do not drive it that much because you will likely cause more damage driving a car with just 3rd gear.

So when my TCM died, I started my engine and then immediately after I put the car in revers, there was a clunk sound come from the transmission, the AT light went on along with CEL. When the AT light is on, it doesn't indicate what gear you are in and manumatic doesn't work. All you have is reverse, and 3rd gear.

According to a senior technician, if you know how to find the TCM, then you can probably remove and replace it and there's no special flashing of it or programming. You pretty much buy the unit, and install it. It should only cake a couple hours. IF this happens again, I know what part number to order from Mazda and I'll print out the factory manual sheets to do the work myself, but hopefully this TCM is better than the last one.

We don't know the cause so I hope this doesn't happen to anyone else because it's a real hassle to have your car break down 40 miles from home and set you back $1K.
 

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oddly, I just had the same code (U0101) for a bad TCM at 102k miles.
They (Tistin Mazda) replaced the TCM under the extended PZEV warranty, so not sure why somebody in california was forced to pay...although I do go to this dealership for everything and I've known the service writer for 8 years now.

the bill was for $663.29 covered completely under the extended PZEV warranty coverage, maybe justified because you don't get good mileage if you're stuck in 3rd gear all the time.
 

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Ils on a beaucoup de Mazda qui ont ce problème avec le code U0101, Comme le TCM est placé directement sur la transmission il est toujours chauffer, et avec le temps il peut avoir des problèmes, Si le voyant AT est fixe Probablement elle est définitivement endommagé il faut le changer, Sinon vous pouvez changer l'emplacement du TCM, Et ça règle le problème définitivement :)et vous économiser beaucoup d’argent;)
voir sur la photo où je l'ai placé
Traduction Google
They we have a lot of Mazdas that have this problem with the code U0101, As the TCM is placed directly on the transmission it is always heating up, and over time it can have problems, If the AT light is steady Probably it is definitely damaged there must be changed, Otherwise you can change the location of the TCM, And that fixes the problem definitively :) and save you a lot of money;)
see on the photo where I placed it
105740
 
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