My D4 blinks as soon as the car starts moving.
The code i get from the 2 pin connector is 2 (2 quick blinks). This is supposed to be related to the lockup control solenoid.

The solenoid has normal resistance, but didn't click all the time when i tested it (sometimes it clicked, sometimes, it sticked)
I bought a new solenoid from the local junkyard and installed it last saturday.
result : no more D4 whatsoever... until yesterday, the same !@#$% started again ! again it is a code 2 (lockup control solenoid)

I removed the solenoid today and tested it and it seems ok, resistance is ok, clicks as it should.

I am clueless now as to what to do, i guess i need to check the wiring to the TCU and maybe the TCU itself... but the strange thing is that everything worked perfectly for 3 days after the solenoid replacement, then failed again.
I remove the backup fuse to clear the fault, but as soon as i start driving the car, D4 starts blinking and the same code (2) is registered.

Transmission fluid is brand new, very clean, i replace it every 10k or less, always with honda atf z1...

Any ideas are welcome.

Thank you.

 

Maybe clean the screen/gasket and solenoids as best you can with throttle body cleaner in case they are clogged.

You can test the resistance at the solenoid, then test the resistance for the same wire(s) at the TCU connector. I am not sure how or where that solenoid is grounded. The connector plugging into that solenoid should have continuity to ground (on the ground wire, don't know the color).

 

i cleaned it well before putting it on the transmission, not sure though if there is no dirt inside the small pipes within...
the valves are grounded through their bodies, the whole valve assembly is the ground, then on the connector, you have 2 pins, one for each valve (a and b)
i'll check at the tcu this week end and let you know
thank you