Hello and welcome to JustAnswer!
Which wire did you run from the IAT to the engine controller?
Do you have a voltmeter to do some testing?
Let's start by seeing what we have going on electrically. Unplug the IAT (the sensor in the air intake inlet. Put the black lead of your voltmeter on ground, set the meter to 200 ohms. Use the red lead of the meter to probe the brown/yellow wire. You should see continuity to ground, but it will have a little bit of resistance. let me know how many ohms you see.
Then set the meter to 20v DC, turn the key on, and check the voltage on the second wire in the connector, the black/red wire. Let me know what you see for this also.
800 ohms is quite alot. I would have expected that to be in the 30-40 range or less. Lay in a jumper to ground on that brown/yellow ground wire, clear the code, and restart the engine and see if the code resets. You've got the correct voltage on the signal wire for an unplugged sensor, so we know the reference voltage from the controller is ok, we know the wire running to the sensor is good (it should be, it's new anyway) This leaves either a bad sensor or a poor ground.
The sensor gets a 5v reference, it runs through the sensor and then to ground. The sensor's internal resistance changes depending on temperature and this is what varies the signal voltage. If there isn't sufficient ground on the other side of the circuit it's going to set this code for "volts high".
Where is the sensor located that you are testing?
The other code is for the ambient temp sensor, also a volts high code. Is the ambient temp sensor unplugged? You've never seen this code?
How did this problem come about? Was there any body work done in the front? Slide underneath real quick and have a look at the wiring harness that runs along the lower radiator support. Is there any damage to the wiring at all?
Try it with your ground jumper. Take a jumper wire from chassis ground (or the battery negtative) and put the other end on the black/red wire. Start the engine up and re read the codes.
When you had the harness apart did you have any trouble with colors? Did you replace one wire at a time? Absolutely sure each wire is connected correctly and no circuits got crossed?