2004 Mazda3 Transmission will not shift after and before new transmission

[Pauly]

I have a 2004 mazda3 2.3 auto (5 door model) My transmission was slipping when changing from 2nd to 3rd gear (no other gears had an issue) after a month it got worse and wouldn't go into reverse. The AT light came on as well as the check engine light. I had no reverse and when I put it in drive it started from 2nd gear wouldn't shift past 3rd. (manual mode stopped working as well) I understand that its now in limp mode from what my mechanic has told me. The mechanic did a pressure check on the trans and told me I needed a new transmission. So I agreed to have the transmission replaced. New transmission is now installed and the mechanic is now telling me that there is still an issue and the car is still not shifting correctly. He has said that he is having a hard time reseting the TCM, (its not responding) he is guessing that its a faulty TCM and it needs replacing. When I went for a test drive with the mechanic with the new trans installed the car is shifting hard into all gears and this is why he is now telling me he thinks its the TCM. Guessing game has started and I give up. At this point I honestly believe that my transmission never needed changing and it must be related to the TCM. I bought the car new in 2004, transmission serviced every 60,000 miles with the car now having 135000 miles on it. So, within the life of owning the car I only changed the trans oil and filter twice and of course now with the new trans installed 3 times. Any ideas as what I should look at? I have already changed the turbine speed sensor and the pulse sensor just for the hell of it. As a side note, some days the car would run fine, with no slipping and perfect gear changes before it went into limp mode / safe mode or what ever you might call it. Strange but true. Google searched for the last 3 hours trying to find an answer. I called the Mazda dealer where I purchased it from and asked if they can help and they told me they would need to check the entire electrical system at $165.00 an hour plus.

[S.F.W.]

If you are located anywhere near the GTA, take your car to Street Performance. Jimmy is the best at resolving issues related to the Mazda3. As well, his rates are the best around.

[Pauly]

Thanks, I'm currently in the USA (Chicago) I'm giving the shop till Thursday then I'm hitting the dealer.

[S.F.W.]

Thanks, I'm currently in the USA (Chicago) I'm giving the shop till Thursday then I'm hitting the dealer.

ah well, I would maybe check on mazda3forums.com, see if anybody knows a good garage in the Chicago area. The dealer, they can fix it for sure, but the cost will be very high.

[pacmann33]

Thanks, I'm currently in the USA (Chicago) I'm giving the shop till Thursday then I'm hitting the dealer.

I'm also in Chicago until Friday, I don't have a vehicle here though, otherwise I would have offered to help you get around while the car is in the shop.

Good luck! The dealer is probably the best option, it sucks when things break and you're out of town.

[TheMAN]

at this point, I'm more inclined to believe it's a wiring problem... don't listen to what your "mechanic" says and get the wiring checked!
there is no TCM in any of the 04-05, and not in the 2.0s from 06-09... it's all part of the ECU... that is expensive too!
any computer related modules must be replaced by the dealer as they come blank

[BigDaddy]

Hi There,
I just had a very similar problem with my 07 hatchback 2 weeks ago where the trans slipped, the AT light came on, the engine light came on then everything went haywire. I has under 100 K and I took it to the dealer to look at and they first thought it needed a new computer (PCM) so they replaced the computer which was still under warranty but the day I got it back the exact same thing happened again and now they are telling me that it is most likely a wiring issue frying the computer but they don't know for sure and they still have it in their shop :S. It's been a major headache so far...if I were you I would lean on a electrical issue over a transmission issue!

Another thing they told me was that the problem with my car is strange to them whatever that mean...maybe faulty part I don't know...

Wish I could be more help!

[shu5892001]

i would take it to a dealer and pay the premium knowing they will take care of it properly

[DualSoul]

i would take it to a dealer and pay the premium knowing they will take care of it properly

Considering some of the horror stories about dealership service in this forum, this may not be the best advice...

[acrossthec]

Hi There,
I just had a very similar problem with my 07 hatchback 2 weeks ago where the trans slipped, the AT light came on, the engine light came on then everything went haywire. I has under 100 K and I took it to the dealer to look at and they first thought it needed a new computer (PCM) so they replaced the computer which was still under warranty but the day I got it back the exact same thing happened again and now they are telling me that it is most likely a wiring issue frying the computer but they don't know for sure and they still have it in their shop :S. It's been a major headache so far...if I were you I would lean on a electrical issue over a transmission issue!

Another thing they told me was that the problem with my car is strange to them whatever that mean...maybe faulty part I don't know...

Wish I could be more help!

Similar problem with my '04 hatch. Jerking at high speeds, and shakes around 60 km/h for a week, and then I get the AT light and check engine light come on, manual mode is disabled and it's stuck in 3rd. Brought it in to Gryo Mazda (where I bought it three months ago) and they're saying it needs a new transmission. I'm just surprised because 1) the car only has 74,000 on it, and only 6,000 of those are mine, and 2) the transmission was fine until a week ago.

However, the body computer fried on me last month, for no apparent reason. So I'm wondering if there's a stray electrical problem that screwed up the transmission via the ECU (per TheMAN's suggestion)? Either way, I'm going to go for a test drive friday after they drop in the new transmission and we'll see how it goes.

[TheMAN]

if the "AT" light comes on, it indicates an electrical problem usually... it's been known that the transmission shift solenoids in these trannys are known to go bad... might not be a lot of 3s with this problem, but a few proteges had these fail, which is the same tranny also except for the final drive difference.... it can be fixed for a couple of hundred bucks with some know-how and a weekend

when the shift solenoids fail, it will usually go to failsafe mode, and that means starting in 3rd gear, but possibly shifting to 4th but NO torque converter lockup
this happened on my corolla beater, and I fixed it for 20 bucks :D

dealers are not usually equipped to rebuild auto trannys nor have the trained persons to do so.... they're more than happy to sell you a reman unit and make your wallet lighter
independent shops are even worse, and tranny shops love to sell you a complete overhaul job


anyway, you definitely need to have the wiring inspected before going further... a squirrel or rat can do plenty of damage!

[BigDaddy]

Good advice! Mazda still has my car (almost 3 weeks now) and is about to replace the third of 3 wiring harnesses (the first 2 did not fix the problem). They claim that will fix it but that's what they said with the first part of the harness then the second :S.

Is it likely that a bad solenoid will also fry the computer? It seems like a bad design if that's the case

[TheMAN]

the BCM is not related to the ECU.... the ECU controls the tranny... the ECU normally has enough protections built in to protect its circuit drivers, so it's very hard to fry it... any bad solenoid or sensors wouldn't fry it, if that was the case, we'll be replacing ECUs all the time as something in the car breaks!

but if there's some wiring problems, it will fry other electronics instead, such as sensors and solenoids

[BigDaddy]

What are some likely causes for an ECU to fry? Right now Mazda thinks its wiring harnesses in my car but they still haven't been able to fix the problem. I'm starting to think it may be something else entirely that they haven't looked into yet