2003 Honda Accord engine code p2646 engine will not rotate 360 but stops.when turned in reverse by hand starter will turn then get stuck and will not turn forward. What is possible causes? Locked?

USA spec car in USA? not told
2.3L inline 4 banger.DOHC +VVT cam. 5sp, M/T
nor real name of the box told.
Vtec is honda name for VVT, valve variable timing, and is not a transmission part at all so is off topic if we want to do 1 at a time.
a wise idea that, leaks are your problem.as all are.
your post seem clueless, here, find a real shop and get it fixed?
vtech bad causes huge engine power loss, for sure stuck in idle mode. so lets end that here.
and talk the box, what box 5 speed is it
not told at all
honda says 5speed is a manual transmission M/T
the silly cable to it is bad.
end story, endless.
2 cables clutch release snapped i gear. makes it hard to shift if you do not move car bay hand to N./ (a trick to lean 2 man job) as all tow truck drivers know for 100 years.
shift cable bad. (or levers to it)
see this first photo , one can drop off links to that #8 part and shift the box by hand, sure can and if can the box end is good .
box means transmission box in whole.,, mech jargon.
all this is pure mechanics 101 problem shifting any M/T is.
photo 2 is lever #2 id and cable set 6
one if bad, looking only finds it as is 100% pure mechanical parts.
end to end. no brains no CPU or TCM brains here, just real gears and levers and flex steel cables that love to fail not lubed regular.











photo

you replaced the solenoid but the code refers to the actuator A bank 1--performance problem or actuator stuck off====causes wiring---rocker arm actuator
have it professionally checked and if faulty replaced , then the code will be cancelled

Not related, first is a transmission output speed sensor code, check the connector, it's probably the reason you have slamming when it s cold.
second code is for low vtec oil pressure, usually caused by low engine oil or dirty/wrong viscosity oil being used.

I have seen issues like this on other Honda's and the problem turned out to be the ignition starter switch. Do this, jumper power directly to the starter solenoid trigger wire and see if the engine cranks.

honda accord code p2646=

rocker arm actuatar system performance or stuck off

Low oil or wrong oil will cause issues with the variable valve timing solenoid as it is a hydrolic valve that used the oil to work when commanded.

p2646 vtec oil pressure switch circuit low voltage - check wiring or change sensor

try this link, i tried to list them but their were to many P2646 VTEC Oil Pressure Switch Circuit Low Voltage

*http://www.honda-tech.com/showthread.php?t=978933*

I'm assuming you have the 2.4 Liter engine. If not, please get back to me. I will paste instructions from autozone.com below, but recommend you also read thru my post at http://www.fixya.com/cars/r5973094-starter_replace and let me know if you have questions.

2.4L Engines
3.0L Engines

NOTE The factory sound system has a coded theft protection system. It is recommended that you know your reset code before you begin.

Remove or disconnect the following:

Negative then the positive battery cables Automatic Transmission Fluid (ATF) cooler Starter cable from terminal B located on the back of the solenoid Black/white wire from the S (solenoid) terminal Two bolts that mount the starter to the transaxle assembly Starter
To install:

1. Install in the reverse order of removal.

NOTE When installing the heavy gauge starter cable, make sure the crimped side of the terminal end is facing out.

1. Enter the anti-theft code and radio presets.

sounds like the timing belt jumped