I changed out my MFD last night, and this morning when I turned on the car everything functions properly but the master warning light was on. What part of the multi function display replacement could have caused this? The MFD works fine, but the banner at the top of the screen is blank with a warning symbol of a car with an exclamation mark. I drive a 2009 Prius. iPhone ?
Where did you get the new MFD? Are you positive you got the right part number? Try putting your VIN into this site. It shows four different part numbers for my car, depending on package options.
If that warning is anything like the Check Hybrid System error in the Gen 3, then it is a very generic message that could've been caused by the electronics detecting the loss of a ground, or an unexpected ground in the system when uninstalling/installing the MFD. If this is the case, then the error will clear by itself after a few (up to ten) starts with no error condition. You can force the clearing by cycling the car Ready, then Off till it clears.
You should have disconnected the 12 V battery while doing that replacement. If you did NOT, disconnecting it for a few minutes now might clear that up. Might not too but worth a try.