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2003 Mazda 6s V6 Automatic w/ manual option

I have a completely random event that keeps happening once in a while and I cannot replicate it at will.

Once in a while driving my car, it will randomly jerk. The "Check Engine" light comes on along with the "AT" light and sometimes the "Traction Control" light. When I use my ScanGuage II to check the codes I get the U0101 and I believe U0100. After I park my car, clear the codes and turn it back on again, it runs like nothing ever happened.

From what I have read it sounds like the connectors on the transmission could be loose, or I have a bad solenoid. I also read that the transmission control module (TCM) could be bad.

Please give me some ideas so I can begin troubleshooting.
 

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I have the exact same problem in my 2004 6s (although I can't yet verify the codes -- I have yet to get a code scanner). Everything works great and then the AT light and CEL (check engine light) both come on. The TX shifts very rough. Once I stop the car and restart it, the problem goes away (the CEL may remain on for a while but it extinguishes after a day or so).


I also found this:
I have a 2002 mazda 6 an i am getting codes U0101 & - FixYa
 

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With codes U0100/U0101 (TCM/PCM not communicating with one another), the shop manual suggests inspecting the wire bundles between the TCM and PCM. I took a look under my dash and found the TCM, but found no visible signs of visible wire or connector damage (although I didn't see the entire wire bundle either -- I still need to remove the plastic shroud below the steering column).

Also, the tx still works through all gear ranges, even in the manual mode -- the shifts are just very rough. The clutch packs seem to engage very hard, with little to no shift dampening -- my concern is that I have to find a place to stop very quickly and minimize further shifting for fear of damaging the clutches and brakes in the TX. I doubt the solenoids are the issue; otherwise the tx wouldn't be able to shift certain gears (shifting works through all gears).

My car has 151,000 miles on it, and this problem has surfaced only within the last 25,000 or so miles. It seems very random, but it is also beginning to occur more frequently. I have religiously changed ATX fluid with the correct fluid every 30,000 miles. I might also point out that the problem seems to occur while driving up a steep hill/mountain for an extended time.

Jordan6i -- I'll check the starter relay and fuse, but how would either of these affect the operation of the transaxle? Have you seen this problem? Any other advice would be appreciated -- thanks!
 

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Yes, I have gotten the same codes from a blow starter fuse under the dash, i would check all the fuses to be sure. It freaked me out like you said it could be the tcm,ecu,pcm. So happy it was only a blown fuse.
 

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Just a little confused here. If it was the starter relay fuse the car would not start. How does that cause a loss of communication

It could be his ride has 'other issues' and that fuse provided some kind of path that normally isn't an issue or helpful to this cause. Think in terms of leakage current, voltage or a path to ground. Likely covering up a bigger issue. :eek: JMO....

With that, I would have to agree as CAN bus communication from module to module needs anything more than power, a ground and a data line. Whether the sensors or connections to those sensors are valid is moot point as this is about the individual modules talking on the bus without error.

I would unplug the battery and then disconnect the 3 key players; TCM at the trans. ECM and BCM under the dash on the left side. Look for corrosion pushed out pins, bent pins, burnt wires, chaffed wires.... If nothing is found put them back and proceed to the connections at the fuse panels. Data does not go through here but if the ground or power to a module is compromised this coudl cause the error.
 

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It could be his ride has 'other issues' and that fuse provided some kind of path that normally isn't an issue or helpful to this cause. Think in terms of leakage current, voltage or a path to ground. Likely covering up a bigger issue. :eek: JMO....

With that, I would have to agree as CAN bus communication from module to module needs anything more than power, a ground and a data line. Whether the sensors or connections to those sensors are valid is moot point as this is about the individual modules talking on the bus without error.

I would unplug the battery and then disconnect the 3 key players; TCM at the trans. ECM and BCM under the dash on the left side. Look for corrosion pushed out pins, bent pins, burnt wires, chaffed wires.... If nothing is found put them back and proceed to the connections at the fuse panels. Data does not go through here but if the ground or power to a module is compromised this coudl cause the error.
lol - prior posts are year old!

^^ Well I hope this helps somebody! :mellow:
 

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I'm new in this forum I have 2004 Mazda 6 2.3 L won't pass the recent smog check, OBDII monitor not ready
Catalyst EGR and /or VVT System and evaporative system I replaced EGR then I check, monitor status shows MIA FUE CCM CAT 02S HTR EGR in green light except for EVA show in red light, now shows code U100 (1/1) lost communication with ECM / PCM "A" car runs well it has power seems like does not have any problem does anyone experience the same issues I need your help thanks
 

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Got the u0100 code today..purchased 2 tcms we on bought as a bet no fix to slipping issue. 2nd one was a reshipp not a purchase sorry for misspeaking. The new one that came had a p/n ending in G. The one on car ends with E would that cause a comms error? I saw some posts that have been quite confusing..the seller stated that the tcm is for 03-04 6s atx. ? Is dont these go in specific vehicles with specific options or are they pretty much interchangeable. If not wound this be the cause of a comms loss being a different tcm? Or was something done wrong. Shop put it in so cant attest to install. Some say it makes no difference some say otherwise...I just want it fixed

Sorry if this is hard to understand Im currently typing from 650ft one handed
 

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I'm new in this forum I have 2004 Mazda 6 2.3 L won't pass the recent smog check, OBDII monitor not ready
Catalyst EGR and /or VVT System and evaporative system I replaced EGR then I check, monitor status shows MIA FUE CCM CAT 02S HTR EGR in green light except for EVA show in red light, now shows code U100 (1/1) lost communication with ECM / PCM "A" car runs well it has power seems like does not have any problem does anyone experience the same issues I need your help thanks
Did you ever fix the problem? I am currently having the same problem. check engine comes on every time they smog it. after 15 min of driving it takes off check engine.
 

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I also have ssme fault surely someone knows fault starter moter relay and fuse under dashboard where exactly are you meaning ? Do you mean fuse box passengers foot side wall under dashboard?
 
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