2010 CX-7 error, U0073:00-28 Control Module Communication Bus off. Help!

Hello. I recently purchased a 2010 CX7 with a 2.5L automatic 5 speed.

I have three error codes, two I know are powertrain/transmission related. The car has a problem in 2nd gear and reverse, and the AT light sometimes goes on or off, and it will not stay in MT. If I start the car and put it into M1 itll shift from M1 to M3 (skip 2) and then switch back to AT in a couple minutes. I think it might be a speed/sensor shift position solenoid/sensor, I have 3 of these types of parts but haven't installed them yet.

1) P0732.00-6C gear 2 Incorrect Ratio
2) P0734:00-6C gear 4 incorrect ratio

The next one is the one that is stumping me:
3) U0073:00-28 Control Module Communication Bus off

What could this possibly relate to?

Thank you.

Vehicle info: 2010 CX7 2.5L
Mileage: 110000 Miles
VIN: JM3ER2W50A0310779
Transmission: 5-SPEED AUTO OD TRAN
Trim: SV
Engine: 2.5L DOHC I-4 ENGINE