Question about 2006 Mazda 3

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I have a 2002 mazda 6 an i am getting codes U0101 & U0073.. TCM not communicating and CAN bus A off The transmission is shifting hard and AT light is coming on. car going into 3 rd gear

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  • Davea Mohammed Jul 04, 2010

    Mazda6 2002 AT light coming on and the car is struggling to pull of.. I did a scan on the car and got these two codes-

    U0101- TCM not communicating
    U0073- CAN connection error BUS A off

    is it my TCM?

  • Davea Mohammed Jul 04, 2010

    I will try as u say and run the different test.. i guess the jumping did not cause it as u said the tcm would have burned right away.. However what i noticed is we removed the TCM and cleaned it up and check all sorders and strangely the car started shifting then it started to act up again .. So something is definietely shorting somewhere either on the TCM or on the Solenoids...

    Thanks again for great support.



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Mazdas have had problems in the transmission area for years and it seems like they would be better by now. TCM module is the transmission module and it usally fritzes out becausr a soiloid shorts out and puts too hight a load on the system. The american makers have had so much troble in the past that thier computers turn the check light on disregard ( turn off ) whatever whent bad and try to drive on without that function. The TCM is under the radio but it's not likly to be bad unless the battery was hooked up backwards, jumped started wrong or other charging system problems. The trans will work with out it's computer but like you point out it shifts hard and you don' have high gear and converter lock=up. Find the different soioids on the transmission and un[lug them on at a time. Sounds simple till you go to do it. The connector has all the sensers and actuators in the same plug. but you can still test them for shorts to ground ( nothing is connected to ground inside the trans, unless it's bad.) then testing each wire to all the others with an OHM meter no wire should be connected directly to another 3 OHM minume. once you find the shorted wire remove them from the plug with a wire plug remover tool and thenput it all together and clear codes and them run it and see whick codes come back in. ( checking to see what doesn't work will help too.) the code discription will tell you what you disconnected and then just do what it takes to follow though on the code repair. ( there's lots of things that can happen. So if it's the lock-up soioid the trans has to come all apart and the rebuild may cost so much that a used unit or a trip to the car lot and trade that problem child in with the wire you found still dissconnected as the car will likly be better with out the bad circuit

Posted on Jul 04, 2010

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  • Davea Mohammed Jul 04, 2010

    Thank you.. for the great advise. I had a transmission expert come in and run test on the solenoids.. he did as u said rub direct current to each circuit and ensure the solenoids were engaging.. What i did have in the pas was alternator problems and yes i did jump the car once.. Would this have cause the unit to go bad ? or other problems ... but thiss was like 6 months ago.

    Also i live in trinidad and tobago would you think that the TCM from mazda 6 in the US would work on my car > the part numbers are just slightly different?

  • John P Schwantes Jr Jul 04, 2010

    The american version is likly very different as we have fuel economy standards and it may have a differnt builder as the mazdas that are on the road here are made in the united states and the one you have could have been built in a different country. The jump starting and altenator problems we'er talking about are Lightning bolt fast. The computer goes like a burning match, ( up in Smoke ) The sensers can be damaged by putting power on them so make sure your on a solinoid. ( the wires are bigger the senser wires are small.) no wire should be connected to ground inside the transmission as they operate though the ground control circuits only power comes in for everything and gruond is controlled by the module. the problem will be found with an OHM meter then disconnect that wire and see what happens. Then code the car again and it'll tell you what you disconnected then find the directions to change that part.

  • John P Schwantes Jr Jul 05, 2010

    If cleaning it up getts it working keep cleaning! The plugs the plug into it are known for troble. The plug can be taken apart with the right tools and the wire ends can be cleaned or replaced. if you plugged it in and it worked good once the parts are likely OK and al your doing is finding the bad connection. Once working then you need to put some dielectric grease in the plug to keep the dirt and moisture out. I've never been to you area of the world but all the roads are paved and reasonably clean, You may be running in a area that I would call an offroad situation. You may have to solder each wire on to the trans connector just to keep a good connection.



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