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Discussion Starter #1
Good day mates,

So I have a 2010 Mazda 3, started up one morning, put it in reverse and there was a double jump and I nearly had a heart attack because of it. Turns out there
was a U0101 error no comms to TCM. After some research changed the TCM with another one (not new) and it was great again, for a day.

The issue i'm getting now, is the AT light comes on with the check engine light, and it only shifts between 2nd and 3rd gear, but not normally, very harsh
shifts. But if I then pull over to the side of the road, turn of the ignition and start again, AT light is out, CEL is still on, but drives as if nothing happened.

Sometimes it'll happen again after a couple days, sometimes the next day, sometimes the same day. I had the code read, was a P0758 shift solonoid B electrical error.
Its really driving me crazy. Could it be the solonoid is bad? Or did I buy a bad TCM? Is it wiring?

If it was wiring it should occur after or during driving on a bumpy road right? That something gets shaken loose or something.

Any thoughts, advice, insight and/or knowledge would be more then welcome.

Thank you in advance.
 

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This happened with my 2008 3 hatchback, it would throw CEL/AT and P0753 (I think), then mysteriously go away.

It was the TCM, had to buy a new one, not all can be repaired and a used one is well used. These are a known problem area on the 3's.

I had changed trans fluid so knew it was at correct level. Was this the same code as with the old TCM?

Could be solenoid, but if fluid has been changed over the life of car, then best guess is the TCM.
 

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Discussion Starter #3
The old TCM just gave the good old U0101, and that one was just like, nope, not today son, i'm done working forever.

This one just seems to play games. I havent changed trans fluid, but since its at the correct level and beautifull red im assuming that wont be an issue
 

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Sure sounds like you are going to be in for a new TCM. You could try having one of the places that repairs them have a go at it. Keep in mind not all are repairable.
 

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Yeah, i'm sort of afraid of that too. Sucks that now i might have 2 shitty TCM's in my possesion. I'm gonna try get the old one fixed and for now just risk frequent heart attacks with the replaced one. Thanks man
 

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Discussion Starter #7
I could do that, but even if the resistance is ok, it still doesn't fully rule it out since it an intermittent problem, right?
 

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Discussion Starter #8
I'm bringing the old one for repair today, since its just laying around collecting dust now anyway. I hope they can fix it. Will post updates as soon as i know more. Since it could be usefull info for others having similar issues in the future.
 

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Not sure where you are from your flag, but here you usually have to send it off to a repair place. Turn time is quick, but it takes a few days of shipping back and forth. Keep us posted, my $$$ is on the TCM. Make sure they explain how they fixed it, if they say it was a software/coding issue, I'd be skeptical that it is fixed.
 

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I could do that, but even if the resistance is ok, it still doesn't fully rule it out since it an intermittent problem, right?
Actually, the opposite condition (where resistance is out of spec) would be more helpful in this case, by most likely confirming a bad solenoid.
 

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Good day mates,

So I have a 2010 Mazda 3, started up one morning, put it in reverse and there was a double jump and I nearly had a heart attack because of it. Turns out there
was a U0101 error no comms to TCM. After some research changed the TCM with another one (not new) and it was great again, for a day.

The issue i'm getting now, is the AT light comes on with the check engine light, and it only shifts between 2nd and 3rd gear, but not normally, very harsh
shifts. But if I then pull over to the side of the road, turn of the ignition and start again, AT light is out, CEL is still on, but drives as if nothing happened.

Sometimes it'll happen again after a couple days, sometimes the next day, sometimes the same day. I had the code read, was a P0758 shift solonoid B electrical error.
Its really driving me crazy. Could it be the solonoid is bad? Or did I buy a bad TCM? Is it wiring?

If it was wiring it should occur after or during driving on a bumpy road right? That something gets shaken loose or something.

Any thoughts, advice, insight and/or knowledge would be more then welcome.

Thank you in advance.
Hello check this video out. Might be a solution to your problem
 

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Discussion Starter #12
Not sure where you are from your flag, but here you usually have to send it off to a repair place. Turn time is quick, but it takes a few days of shipping back and forth. Keep us posted, my $$$ is on the TCM. Make sure they explain how they fixed it, if they say it was a software/coding issue, I'd be skeptical that it is fixed.
The flag is from Suriname, South America. Here you just have to be lucky enough that there's a guy that can fix it. Brought it somewhere yesterday, but the guy said he can't fix it because of the seal thats on it, says that when peeling it off there's a significant chance something might break or the board might break taking it out of the aluminum housing. So my search continues. And sending it to the USA would in the end probably cost me almost as much as a new one, even though I havent found any place in the world that sells the partnumber i need yet.
 

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Discussion Starter #14
Hello check this video out. Might be a solution to your problem
Thanks, I saw a couple of these places online, but the problem is that I live outside the USA, and sending it in from here alone is gonna cost a lot, and if then they say they can't repair it, well then i'd be sitting in a corner crying like a toddler i think.
 

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Discussion Starter #15
Ok, so repairing doesnt seem to be an option. The mechanics who repair them say that because of the resin coating it cannot be done or is near impossible. The chance of damaging it while removing the coating is 90% and to peel it out of the aluminum casing is an even bigger risk, so they dont wanna touch it. They also stated that those send in repair people probably just break out the old board and put in an aftermarket third party one, especially since they get it done so rapidly. Sort of made sense. SO, long story even longer, I think i'm gonna let an electronics guy check the wiring, to see if there isnt anything fishy going on, if that seems ok, then I think I can 100% for sure say I bought a shit TCM.

But I'm thinking the TCM just isnt compatible as well. My engine type is MZR Disi, which is only sold in europe and japan, and I believe australia and new zeeland as well, so I'm thinking that the one I bought in USA is made for a different engine type. I also notice the shifting moments are off sometimes. It takes to long to shift from first to second, and from 4th to 5th. I'm used to it shifting under 2000rpms when driving gently, but first to 2nd is at about 2300 (which is still ok) but 4th to 5th is at about 2500 and above. And maybe, the ECU expects the TCM to shift at different timing, that they sometimes piss eachother off and blame the solonoid. I'm just thinking out loud though.
 
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