Have someone take a look to see whether there are any current trouble codes or if any codes are in the "history".

Limp Mode is the computer's response to a problem it detected that could cause damage to the engine or transmission. Limp Mode severely restricts engine power, and it sometimes limits the transmission to the lower 3 gears. Again, it's all to protect the engine/trans from even worse damage, but allow the driver to move the vehicle to a safe location (off the highway or leave the highway at the next exit. Jim