While driving 40-50 up slight grade. Trans still locked in 4th. I detect what could be called a misfire, but it is too subtle to actually be a misfire. More like a shudder. If TC unlocks or trans shift, it stops.

I would say you have more that one code fault and they just used a cheap scan tool. You need an auto electrician with a pro grade scan tool computer. That is the only thing that can diagnose the engine speed sensor.

https://www.google.com/search?q=auto+electrician+near+me

What the P0304 code means. The P0304 code will be seen in cars where the ECU has detected that cylinder 4 is not firing properly. The ECU monitors the operation of all cylinders to ensure they are all firing on time, so when one misfires repeatedly, a Check Engine Light is set.

P0304 OBD-II Trouble Code: Cylinder 4 Misfire Detected

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P0150 = O2 Sensor Circuit Bank 2 Sensor 1.
P0300 = Random/multiple cylinder(s) - misfire detected.
P0304 = Cylinder 4 - misfire detected. You will need to get the car locked at in more detail to find out what it actually is.
You will need to recheck the P1931 code as I cannot find it listed.

Sounds like a tooth missing of the fourth gear, check trans sump for metal filings or pieces. if auto, adjust bands and check/change fluid and filters. as well.

replace no 2 injector

Before guessing at transmission problems, check the fluid level (car warmed up, engine running in Park on level ground) and have the PCM scanned for trouble codes FIRST. This guide is meant for problems that do not show up as PCM codes (like shift A&B solenoid failures, for example).
Also note that many problems that show up as transmission issues are actually PCM or electrical, and may be external to the transmission. Try a different PCM, and check for chafing where the cables come out of the PCM.
What is "limp-home mode" ? This is a fault mode in which the transmission either loses electrical power or the PCM deactivates all of the electronics. The transmission will default to max line pressure. The driver will have Reverse and 3rd, with manual 2nd available by putting the gearshift in 2 or 1 (doesn't matter). 1st, 4th, and TCC lockup will not be available. It will not hurt the car to drive it like this for short periods, but use manual 2nd to get the car moving, and be aware that the trans will generate more heat than normal while operating in limp-home mode due to increased torque converter slippage during 2nd gear starts and no lockup in 3rd gear.
No 1st or 4th available; trans shifts 2nd to 3rd by itself in D or OD and locks the converter : ShiftA solenoid failed. Easy fix in the pan. Or a wiring problem from PCM to trans.. or PCM.
Trans shifts into gear harshly, car feels sluggish off the line, No 1st, 4th or TCC lockup available, Manual 2nd, 3rd and Reverse are only available gears, CEL is on: Transmision is either in limp-home mode or has lost electrical power. If there are lots of error codes in the PCM, check the underhood fuse that powers the transmission, and if it pops again, look for a short in that circuit like an O2 sensor harness touching exhaust. Otherwise, check PCM codes for a particular fault in the transmission causing the PCM to put it in limp-home mode.
Thank you for using fixya and good luck. Check all your fuses first to ensure it's not a simple as that before you take it to a transmission shop. Call around, most transmission shop will scan free of charge to inspect the condition of your transmission.

Get your ICM and coils tested first. This is a common problem that seems like a transmission issue.

Next, when was the last time your spark plugs and wires were changed? This may cause one cylinder to misfire intermittently.

If this was a vacuum modulated transmission, I would normally suggest checking the lines but the 460e is computer controlled.

Check your 'kickdown' cable from the throttle to the transmission.

If none of these easy fixes work, there is not a lot more you can do other than repair or replace the malfunctioning transmission.

Good luck!

DTC P0734 is "4th gear incorrect ratio" - that's your torque converter 'LOCK UP Clutch" It's worn out (or you're using the wrong Trans Fluid required by Hyundai - SPIII OR Both). The P1624 is simply the Trans Control Unit (computer) communicating to the Engine Control Module (ECM computer) MIL - on request signal to ECM = asking it to turn on "Check Engine" light. MIL = Malfunction Indicator Lamp. When the torque converter 'lock up" clutch slips or doesn't engage, the trans automatically returns to 3rd gear and stays there (it's called 'fail safe' mode) until you cycle the ignition key, then everything resets until the malfunction occurs again.
You'll need to have an AT (Automatic Transaxel) tester hooked up to verify this. Hyundai has a Service Bulletin specifically for "gear incorrect ratio' codes. If when you changed the trans fluid, was it done at a Hyundai Service Center? If not, someone may have installed the wrong fluid.

take sample of your fuel into clear plastic bottle from fuel line
is there any water present?
this can cause these codes and then not go on storing codes for other bank even though that bank will be missfiring also due to water & P0300 Random/Multiple Cylinder Misfire Detected being logged
check all connections to coils/leads & wiring connectors
due to miss fire codes for cyl 1,3,5 all on the same bank
also look and check for air leaks on that bank (hose knocked off or splithose)inlet manifold gasket,brake booster etc...
3 injectors being blocked slightly on same bank posible!!!
check wires and signal

was it running like this b4 tune up & repairs?
this is what codes are
P0170 Fuel Trim Malfunction (Bank 1)
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0305 Cylinder 5 Misfire Detected

the last code is for trans due to misfire/running lean on bank 1 probably a torque problem code

Honda transmissions,as well as most other overdrive transmissions,should be driven at all times in drive 4,or the overdrive position,with the exception of severe driving conditions,such as towing a load,extremely hilly terrain,or long uphill grades,the trans should be taken out of overdrive,and placed in the drive 3 position.This is to prevent the perpetual shifting back and forth of the trans from 3rd into 4th,back to 3rd,back to 4th,back to 3rd,that would eventually damage both the 3rd and 4th gear clutch discs and components.