this is just an FYI....twice in the last 6 months, my 2014 with 280,000 KM has had an issue where I go to leave for work in the morning and the transmission shifts VERY hard, like a BANG, or won't shift at all, and there is a serious lack of acceleration
The fluid is good, has always been religiously changed, and was recently changed..... the last time this problem happened, I topped up the level with about 1/3 quart of fluid as it looked like it may have been a wee bit low.....best i could tell it was at the lower line on the dipstick....problem went away.
The first time this happened, I went straight back home and did a drain/refill, drove around a bit, no issues, then for good measure I then sucked out and replaced an additional 1.5 quarts of fluid which I replaced with Royal Purple. Problem disappeared.
The last time this happened I checked to see if threw any codes with my OBDII reader and it was showing a Pending code of P0776 which is defined as: Pressure Control Solenoid "B" Performance/Stuck Off

The Transmission Control Module (TCM) uses Pressure Control Solenoids to control the hydraulic pressure in the transmission which is needed to apply the various clutch packs in the transmission that provide the different gear ratios needed to efficiently propel the vehicle down the roadways. When the TCM detects a pressure control solenoid is not performing as desired, it will set code P0776.

Anyway, again, just a PSA for you. But I should ask, if anyone has had the same issue, do you know if Pressure Control Solenoid B is a replaceable part? I am going to guess no.....

 

I believe the 3rd gear solenoid has been an issue on these transmissions. Some have replaced it and it worked fine after. There are a couple of videos on YouTube that shows procedure. Doesn't look too hard.

 

I had this issue with my 2012 Acura TL which uses the same 6 speed AT. It would not shift into 3rd and eventually (as I tried to get home) flashed the transmission light on the dash went into limp mode. I believe it was locked in 4th gear which I used to get home. OBDII read P0776 which is solenoid B as you described. Unfortunately, for these transmissions, the shift solenoids are designed as a one piece unit (4 shift solenoids and 3 pressure switches) and cost ~500 dollars give or take 100 depending on where you get it. My car had 250k miles on it. I was going to replace it myself until I read an article in Transmission digest (found this article while going through other Honda threads for P0776) where the mechanic replaced the high dollar solenoid pack and it didn't fix the problem. The problem was a blown out O-ring in the 3rd gear clutch pack that was found after tear down. The o ring leakage was bad enough that it wouldn't let pressure build up enough to shift to 3rd.

With all this info and not knowing much about auto transmissions, I towed ti to a reputable local transmission shop. He installed a rebuilt transmission from a Honda Pilot for 3200$. During his checkout, he applied power directly to solenoid "B" and it would click indicating it should be operating. So he suggested the problem was deeper in the transmission.
I said all this to warn you that there is no single "B" solenoid to replace to solve this problem because of the multi-solenoid unit design and replacing this expensive part may not solve the problem. I suggest you take it to an expert. There are many old YouTube videos where the older designs would allow the repacement of a single solenoid on older Honda/acura's but we have the new/improved design. The solenoid pack part number for your car is 27700-5B7-000.

 

OK thank you.
This is concerning.
Also, I had called the parts guy at the local Acura dealer who told me "pressure control solenoid B" is not replaceable just by itself, for that one you have to change the whole secondary valve body which has the same part # as the one you gave me (27700-5B7-000) priced at 500-600 USD
I was a bit skeptical of this so I called 2 other dealers and they gave me a part # of 28600R94004 costing 135 bucks Canadian (so about 100 USD)
She also told me its the same solenoid as Solenoid "A"
However, I have a feeling I will have to replace the whole secondary valve body as you indicated. I plan to take the car to a local tranny shop who has a good reputation.
Its not happening often enough just yet but I'm sure it will happen again soon. Also my mechanic didn't think I would need to worry about the fluid filter in the pan being clogged/dirty. i have the diagrams to find the solenoid but my back problems won't allow me to bend over like that working in the engine compartment.

 

Update....I replaced 3.8 litres of trans fluid (drain/refill) and reluctantly added Rislone Transmission Fix additive. It had been giving me sluggish shifts earlier today. Now its shifting with no hesitation in all gears and seems to be working great. The fluid has been drained/refilled literally 3 times in the last 60,000 miles. Hope it stays trouble-free for awhile.