There are several areas that will need to be tested such as trans speed and vehicle speed systems, solenoids in trans etc. The items you can check that often cause these codes is transmission fluid level, tire size and condition. The 2 most common problems that cause these codes relates to tires. The first being condition, make sure all 4 tires are the same size and same amount of wear, if the average circumference deviates too far from the norm then the computer may think the gear ratio's are off in the transmission. Second compare the actual tire size on the vehicle with the tire size chart on the door placard. Come to think of it, you should check and adjust the tire pressures to the spec on the door placard also. Another less common issue is if the computer has been replaced or re-flashed then the wrong gear ratio may have been programmed at that time.
Often this is a result of an internal mechanical failure. What is happening is that the computer calls for certain gears and expects those gears, but others are actually being used. You will need a good transmission diagnosis.