My 2005 accord lost power and it give a code 2646 ,what could it be?

code p 2646 refers to rocker arm actuator A bank 1---performance problem or actuator stuck off=== causes wiring--- rocker arm actuator
discuss the problem with a service dealer shop or an accredited service shop that has experience on your make of vehicle
with rocker arm problems , to stop rotation it may be bottoming out on a valve spring and not letting the cam shaft turn .
talk with a shop for a proper diagnosis and quote

Owen, is the engine light on or any codes stored in computer as this info would be beneficial in diagnosing problem.
My guess is your catalytic converter has begun to plug, which gives excess back pressure, robbing engine power.
check the links below.
Signs of clogged bad catalytic converter

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwinzMW8mIXLAhXGMhoKHaWUD_sQFggeMAE&url=http%3A%2F%2Fwww.dummies.com%2Fhow-to%2Fcontent%2Fhow-to-troubleshoot-catalytic-converters.html&usg=AFQjCNE0zpmy0RHqRLsWNF2M6dO2xOkFHg

6 Symptoms of Failing Catalytic Converter DoItYourself com

Symptoms Clogged Catalytic Converter Loss of Power

post now , 100s of times, try searching.
in short , you failed to read the operators guide, for sure.
it tells you this.
1: new car, put code card in BR dresser.
2: write the number (ask radio when working) in the opr. guide, on last page.
3: if lost , only the dealer can give it to you, or IN USA? any key shop with he specical license to do so.
sorry there is no WIKI-Leaks.com on radio codes.

my guess you lost this free book?
http://justgivemethedamnmanual.com/honda/honda-accord-owners-manuals/

all it takes is a dead battery and the world is lost.... sigh...
wow, first ever post here of a photo and for sure clear. wow.
you will go places fast,
yes , you lost the operator guide, (the PO did, im sure the dork)
so get one. never drive a car and for sure this hightech ones.
with no opr, guide. it has lots of very important facts for getting out
of trouble, and #1 is standardized. (IMMO failures? ouch)

the cars that have radio codes, and i presume nav unit.
the car came new with the code cars,
PO (previous owner ) lost it.
the guide says, write it down in the opr guide. i bet he didnt.
so the bad news. its here.
but good news its here (mostly....)
http://justgivemethedamnmanual.com/honda/honda-accord-coupe-owners-manuals/
rats, the navigator system pages are missing.
as you can see the radio codes missing ploy is the same as NAV

solution, (only) (or licensed lock smith shops)
https://radio-navicode.honda.com/

I don't think you will find this online; the dealer can find it for you but probably won't do it free.
If you lost the radio because of battery change or disconnect, you can prevent this from happening again with a cheap, simple device that uses a standard 9 volt battery and your cigarette lighter/power jack, to supply 'keep alive' voltage while disconnecting the main battery. Auto parts stores carry them.

pull code from light ob2 parts store sells it it will give you the code of whats wrong with your car then tell me what code says and ill help you from there

Just give the dealer a call and give them the VIN and they should be able to help you.

Check owners manual, made written on inside of covers or on radio pages.  IF not check inside of glovebox for four digit code.  If not luck, remove radio document all number, ie serial number on unit and call local honda dealer.  They must run the VIN and radio info back to the motherland to get lock code.

I have a 2005 accord, and this worked for me.

1)Turn on engine w/ radio off. Push and hold down buttons 1, 6, and power.
2)I got the letter "U" followed by 4 numbers and then letter "L" followed by 4 numbers; write down those numbers.
3) Go to Honda.com
4)Click on Owners home link.
5)On that page you should see an option for retrieving radio codes for honda/acura
6)you will need to enter Vin#, home phone number and zip code fo the original owner. This will then give you the radio code..