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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

  • The P0722 is likely because the output shaft is not turning when it should be. It seems plausible that the output shaft is not turning, which is why the car no longer moves. Start checking the powerflow. Likely failure candidates are the pump and the torque converter. – SteveRacer Mar 22 at 3:41
  • I'll be honest, I'm not super familiar with what you mean by check the power flow but I do know that after checking the cooler lines there was next to no fluid flow through them. – Gabe Wisneski Mar 22 at 4:12
  • Also, I've just removed the torque converter and found that only a small amount drained out of it, though I don't know if this is normal or not, and one of the sides of the impeller has a lot of side to side play. Again, I don't know enough to say whether or not it's normal – Gabe Wisneski Mar 22 at 4:15
  • A bad pump will not fill the torque converter, which means no power flow. The side-to-side play probably isn't meaningful, as it is supported by the splined shaft when installed. – SteveRacer Mar 27 at 2:44
  • Would a pump failure support the sudden failure? Also after removing the converter it did seem like there wasn't a ton of fluid in it – Gabe Wisneski Mar 27 at 10:31

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