Rep Power: 0

My mom owns a 2018 Honda civic coupe(I believe the trim is an LX). The car has about 96,000 miles on it. She went on vacation with family and came back about a week later to a dead battery, jumped the car and it ran fine all the way home which is about 2 1/2 hours. Within a week or so it had died again. I replaced the battery and the car was fine for about a month. She was getting ready to leave my house and let the car run for a couple minutes to get the inside cooled off. She pulled away and just about every warning light came on, abs, electronic parking brake, traction control, transmission issue and I'm sure I'm missing some but pretty much every warning on the car. The car also started to jump like you are pumping the brakes once you reach about 30mph. We attempted to reboot the system by holding the power button, also we have unhooked the battery and reconnected, erased all codes and after a minute they all come back. Our mechanic who has his own very successful shop and has been a mechanic for 30 years including at shops and dealers replaced the alternator to see if maybe that was an issue and it did not fix it. He recommended us take it to the dealer because he was completely dumbfounded so we did, they ran a diagnostic and pretty much said they didn't know what the issue was so they didn't even charge us for the diagnosis. The only answer they gave was to spend $7,000 to replace the transmission and wiring harness and hope that fixes the problem. We are at a complete loss as to how to proceed so I am posting here in hopes that maybe someone else has had this issue and could give me some advice better than spend a bunch of money and hope it works. I'm not a mechanic but don't understand why every warning light would come on if it's a transmission. I appreciate anyone's help and am open to any advice as this is my first time on this forum. My mom is just lost on how to proceed.

 
Rep Power: 367

when a Christmas tree lights up on the dash, it's low electrical power (electronics go haywire with that)
now, a mechanic could not pin point the issue, dealer could not either... strange...
lots of stories about wiring chewed up by rodents, something is not let charging happen or parasitic draws somewhere, but they should have looked into that.

put multimeter into the fuse box and start chasing parasitic draws?

check if charging is happening? Looks more like a parasitic draw somewhere, though. (short circuit)

 
Rep Power: 0

I agree I figured they would've looked into it. I am not a mechanic but assume it would have to be electrical somewhere. It's been one of the most stressful and strange car issues I have dealt with. I will try your suggestion tomorrow.

 
Rep Power: 512

double check the battery connections. Had a christmas tree dashboard a couple months after I got my car from the dealership. Took off the battery terminals, reconnected them and made sure they were snug, lights went out after 15 minutes or so of driving. Only got the christmas tree again after I wired in my HID relay harness bc I didn't tighten something down well enough.

 
Rep Power: 222

Triple check the battery connections

 
Rep Power: 0

Would you be able to help me with some instructions. I have heard to connect the multimeter to the battery and pull each fuse to see if it changes the pull. Is there a separate way to just check the fuse box specifically. Sorry if this is a dumb question but i just wanted to make sure i know exactly what im doing and what to look for. Thanks.