2015 Civic LX CVT with U0101 code

sparky73

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Hey all, first time poster here and it seems my problem is incredibly unique. I've been scouring for any info on someone who has had this issue but am not finding much. The car runs great, I just noticed it was not getting as good gas mileage as it should, (maxing out at maybe 29mpg highway driving conservatively) so I started to investigate.

As the title says, my 116k miles '15 LX Sedan is throwing a U0101 code: "Lost Communication With Transmission Control Module (TCM)" and there is no Check Engine Light active.
I have read that on other cars with traditional transmissions this would make the car be in "limp-home" mode and not shift, as well as reduce fuel economy. I haven't noticed any oddities in "shifting" but this is my first CVT.
CVT Fluid was changed at 102k, planning on doing that this week as well.
I also checked for any open recalls regarding the TCM, but there are none.

I've also heard that it could be a grounding issue somewhere along the way, but I'm not sure where to begin with that, either.

Any input would be appreciated. Thanks!
 
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Any input
First thing I would do is run to a place like auto zone, advanced auto, orielly's, etc. Have them run a battery test to make sure it's 100%. Some people have gone through 4-5 batteries in a matter of a few years. A bad battery can supposedly throw that code, so it wouldn't be crazy to hear it was the battery.

I realize this video is a 2020 civic, but you can see how this diagnostic tool will likely be needed, unless you just throw parts at the car to see what works. Start with checking the battery though.


View: https://www.youtube.com/watch?v=D5aUH_iTDgA
 
Thank you for your response!
First thing I would do is run to a place like auto zone, advanced auto, orielly's, etc. Have them run a battery test to make sure it's 100%.

I actually did recently do that at an AutoZone, they said the battery is good, but there was an issue with the alternator. They weren't very specific, and it was the staff members' first time using the device so I'm not completely convinced. Also no battery light on the dash (indicating its not charging) either. They were quick to offer me a price for a remanufactured alternator, though! I'll go to another auto parts shop and get a second opinion.
 
I'm glad I got a second opinion! The associate at Advance Auto went over the test results with me, and it said the starter, battery, and alternator are all in good condition. Yesterday I cleared the code with my BlueDriver, did some mixed driving (city/highway) today and they have not returned.

Troubleshooting before this, I also replaced an oversized interior fuse - #2 ACG (Alternator Current Generator) it had a 15A fuse installed when it calls for 10A. It wasn't blown/bad, it was just suspicious. Not sure why a previous owner would do that. Sorry for not including this in the initial post.

Either way, problem solved I guess! I'll keep an eye on it moving forward. Thanks again!
 
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