Fusefinder

I have a 2001 Honda Accord EXL 3L V6 AT who's issue is a long high RPM first gear then a hard shift. 2-3 a little but not as bad. If I baby it (ease up on pedal quite a bit) until warm it runs OK...if I don't I get a TCM light comes on.
The codes are:
P0720 Powertrain- Transmission - Output speed sensor
P1751 Powertrain- AT Hydraulic system malfunction Wiring, range position switch ECM

I have done the Transmission fluid changes at every oil change since I've had the problem also added 2 cans of seal conditioner. I purchased with 176K miles now 192k miles. 8 months at 188k miles after purchased started having issues.
I'm thinking about replacing the internal filter, doing 3- 50 mile fluid changes and pulling solenoids and checking screens associated with them. Any other ideas or solutions before taking it to a rebuild or replacement?
Thanks!

MAD_MIKE

P0720. NC sensor, Countershaft Speed sensor.
Simple fix. Either there is ferrous material on the end of the magnetic pickup and it needs to be cleaned or the sensor is out of range.
Check that the resistance of the sensor is 400-600Ω.
If it is within resistance, pull the sensor and verify it is clean of slurry. Wipe it off and reinstall. If it is dirty, then this was most likely the code issue.

NC is located on top of the transmission towards the end. If it is coated in ferrous material, it would be a good idea to also remove the NM sensor and clean it as well. This sensor is located on the front of the trans case pointing toward the radiator.

Reset PCM and go for a drive.
P1751. Mechanical Problem in Hydraulic System
If this code occurs in conjunction with another code, fix the other code first before investing any time into P1751 issue.
First part is good.
Second part is bad.
'Seal conditioners' will often cause a seal to swell and soften, this is horrible for the transmission, these can cause leaks and internal seal issues, not fix them.
The only thing you should only ever add to trans fluid is a cleaner or solvent to break down sludge and varnish that can cause solenoids to stick.
If you can locally find Sea Foam TRANS TUNE, add that to your next trans fluid change.

Internal filter requires removal of the trans and opening the case.
Removing the solenoids and verifying the screens are clean and goo free is a good plan. But avoid any 'seal conditioners' in the future. They are usually thick goos that only gum up the works. Use the correct ATF or a cleaner/solvent, no 'conditioners' or 'leak sealers'.

VeeSykkz

mine does the same thing. Check your PASS SIDE MOTOR MOUNT. Replacing mine completely cleared up that slamming shift. Ive never liked that long 1st gear. Always worried me.