2001 kia sephia slips out of gear. Trouble codes P1500, P1624, P0740.

Low fluid or too much ATF? (foaming it up and killing bearings)

p07xx is tranny DTC codes. (errors)
TCC lockup failure. (the TCM commanded the lock and
the tail shaft sensor did not rise in RPM
that is the engine RPM does not match tail RPM or 1:1 ratio.
which is LOCK ratio.

1500 is speed sensor , reads wrong,
No Vehicle Speed Signal to TCM.

1624 means.
MIL Request Signal from TCM to ECM.
the means simply the Tcm SAW and error and sent that error up stream to ECM. creating 1500.
remember the ECU never knows what part is bad.
NEVER ! it only knows, the tests failed. (monitors)
the first thing i do is find out which VSS failed.
on some cars there are 2 to 5
the first speed sensor is RPM does the scan tool show correct engine RPM? y/n
if yes,
does the scan-tool show correct MPH? sensor 2.
y/n if not fix that first.
the TCM function (tranny brain must not be lied to, in this order)
engine RPM , MPH.
and last the tranny its self as VSS (rpm) sensors. 1 to3.
my guess, (too lazy to look it up) has 1 sensor on the tranny tail.
if all is good and 1500 means VSS 2 tranny tail is fibbing.
then its one of 3 things.
(all others good)REMEMBER the TCM does comparisons to all speed sensors to shift the car correctly so the front sensor count first. then last the rear.
VSS2 lies. this is bad bad tranny (slips) bad wires to VSS2 or bad VSS2.
most TCM go to limp home when the tranny slips to stop burning up the clutch packs. may skip gears too.

now what does slips out of gear mean. a neutral FLARE?
or down shifts,
if the tranny ever slips. this is bad news.
if it does slip 1500 is only the warning that it did
it say RPMs go out of control and threw 1500 pronto.

Try to think(sic) like a TCM what would you do if the tranny malfs.
answer, throws codes.
and goes to limphome, if necessary, (FSM show these facts)
so does alldata dot com
what i do is try to get tranny to slip. using all gears.
if it slips ,its bad.
The TCM can not run a slipping tranny.
the TC does slip, but the TCM has that all figured out. (modeled)
not locked, and locked it must not.
good luck and do ask questions.