I have a 2003 Honda Accord v6 coupe with a 5 speed automatic transmission - code baya. I recently had the transmission fail on me extremely suddenly and left me stuck on a highway. I want to stress right away how sudden the going of the transmission was as it had never before failed to engage any gear and it had never slipped into neutral during an up or down shift. Anyways, during a drive on a highway I gave it some more throttle to get moving a bit more and it went into neutral and proceeded to rev up a bit before popping into 4th gear I think. I noticed this and decided to check if it was a fluke or not by trying to get it to go back into 5th. This time it did the same except it took a little longer than previous to get back into gear. I also noticed around this time that my transmission temperature guage was noticably cooler than normal highway driving temperatures. I think it was about 140-160F where it normally sits at about 180-200F. So this long shifting happened once or twice more and than the next time it tried to shift it came out of gear and has never gone back in since. At this point the D indictor was flashing and the abs, tc, and check engine light were illuminated. After getting it home the codes was a p0720? for issue with the output shaft speed sensor. This later became no signal from the sensor during testing, a p0722.
After reading Honda's service manual and reading that these codes CANNOT be caused by an internal failure in the transmission, only electrical, I replaced the sensor. It still didn't fix it however and the code remained.
Anyways, TL;DR I am curious as to what the issue may be with my transmission. Here are the symptoms/notes:
Extremely sudden failure, completely within the span of 5 miles at highway speeds fro start to finish
No issues beforehand
Initial sign was by transmission dropping into neutral between shifting, delayed shift, that progressively became worse until failure
Lower transmission fluid temperature than normal, low flow? No flow?
Transmission no longer engages any gears, or even seems to attempt to
Threw code P0720 intially and P0722 during cel clear and testing
Output shaft speed sensor replacement made no change
Transmission fluid level was perfect after stopping
No obvious metal in fluid during drain
No obvious debris in external filter during inspection