Check engine light is on and diagnatics show the error codes, P0722 and U2108

It sounds like the issue with your 2011 Hyundai Elantra might be related to the output shaft speed sensor, especially since you're getting a P0722 error code. This sensor is crucial for the transmission's ability to shift gears correctly. Since the transmission was working fine before the engine replacement, it's possible that a connection to the sensor may have been disrupted during the process. I would suggest double-checking the sensor's connection and wiring for any signs of damage or loose connections. Also, ensure that there's no physical damage to the sensor itself. If everything seems intact, it might be a good idea to have the sensor tested or replaced.

Hope, code PO722 Output Speed Sensor No Signal.
Possible trigger for code,

• Defective Output Speed Sensor
• Defective Shift Solenoids
• Defective Engine Coolant Temperature Sensor
• Defective Valve Body
• Dirty transmission fluid that restricts the hydraulic passages
• Defective Output Speed Sensor wiring or connector

P0722 Ford Output Speed Sensor No Signal
http://www.autozone.com/repairguides/Ford-Freestar-Monterey-2004-2006/Diagnostic-Trouble-Codes/4-2L-V6-VIN-2-Auto-5/_/P-0996b43f802e829c

you need a better mechanic that traces ALL of the possibilities of each code, not just read the code and trow in a part hoping that it's fixed ~ it can be wiring as well, not just plug in a new part as mentioned on the 2nd trouble code to the vehicle speed sensor

P0744 Torque Converter Clutch Circuit Intermittent


P0722 Output Speed Sensor No Signal

the first of the 2 looks to be more intensive to trace and find out the problem & the 0722 is the easier job for an intermediate mechanic to trace the wiring for continuity

p0722 is the out put speed sensor, which controls the speedometer, threw the ECM. And will cause a limp mode which yo went threw. It could be nothing. If it were mine, I would pull the speed sensor and look at it. If there were slivers of metal on it, I would pull the transmission and find out what is getting chewed up before it just died on me. But I build them. If it just had black/normal wear, I would check to plug for corrosion and the the entire system of the car on a scanner.

No output speed sensor signal at transmission output shaft.

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.

The P0700 is not a true fault code, it just means that the powertrain control module has requested the Transmission control module to turn on the check engine light to alert you of a fault. The P0717 is the one you need diagnosed, it is the real problem,.

P0722: Transmission speed signal missing.

There is a turbine speed sensor that detects and reports the speed of the transmission shaft to the computer to help determine shift points. Sometimes this duty is shared by the VSS (vehicle speed sensor) but if your speedometer still works, then the VSS is good and you should replace the TSS (turbine speed sensor). I would guess you are either stuck in 1st gear all the time or your transmission shifts erratically.

p0722 stands for output speed sensor, this sensor might be in need of replacement, p0717 is for transmission turbine speed sensor, P0717 code comes with the following symptoms: engine cutting out, misfire and hard start after the engine is warmed up. check the coil plugs which is the equivalent of spark plugs except it does not have any plug wires. Start with the mileage and if the engine has over 100k miles, usually the coil plugs are worn. You can check it by checking the coil plug wells on the valve cover. If soaked with oil, the coil plug is normally shot and this goes the same for the valve cover gasket. Apparently, when the valve cover leaks oil, it is deposited in the coil plug well and starts shorting the coil plugs because of the contaminated oil. Note: when changing coil plugs, always replace them ALL as a set.

The P1700 is just a request for the check engine light, and this is caused by the U2108. The U2108 is basically telling you that the Electronic Brake and Traction Control Module (EBTCM) is not communicating with the powertrain control module, or the transmission control module.
The very first thing we must do is verify that the fuses that power the ebtcm are not blown and that they are powered. At this point I would like you to verify that the fuse labeled ABS in the fuse block is not blown and that it is powered with the key in the on position.
I would also like you to verify that the fuse labeled V1 inthe power distribution box is not burnt and that this is powered also. After this we need to move to the ebtcm to verify that you have voltage at pins 15,17,18 and that you have a ground at 19 and 16.

This would verify that the ebtcm is getting the proper voltage supplies to operate. The end result of this may possibly be a faulty ebtcm, but at this point we really need to check these items prior.Feel free to contact me with any questions at this point! Thanks!