All I can say is the Axxess box that comes with the metra kit is rubbish. I know some people seem to have no trouble with it, but plenty of people do have problems getting it to work at all.
Here is what I did.
( first of all I better say that I use to be a car stereo installer and had my own business )
( I had read that there were problems with getting the Axis box to work the AC/heater controls. ), but I thought I would go a head and buy the Metra kit anyway as I did not like the factory stereo head unit.
So after I had fitted the Metra kit and everything was all in and working, so I thought. When I tried to use the A/C and heater, they did not want to work properly.
The fan control would not work at all and the heater would stay on full heat all the time, but the rest of the control worked ok.
First I thought I had done something wrong, so I checked all the wiring, all was ok.
So I pulled the stereo out and connected up the factory stereo again to check that all the controls were still working ok, and yes they all worked fine.
So my conclusion was that the Axis box was faulty. I guess I could have tried to send the kit back and tried another Axis box, but because I live in New Zealand, I was not prepared to pay for the postage back to the US.
So What I ended up doing was to strip the original stereo down to the two main circuit boards that are inside the stereo/front panel.
Once I had the two main circuit boards,I had to do a fair bit of rewiring to get the two circuit boards to work together and be able to lay them flat, one on top of the other. I made up a box to fit them into. I then found a place in the car to fit the box. I also had to extend the factory stereo wiring to be able to plug it into the new control box. I also had to extend all the wiring from the box back upto the A/C heater controls etc.
So now I have a better stereo in the car, and the original stereo circuit boards control the A/C - heater etc.
This was my way of fixing the Axis box problems. Its not the easiest way to do it, but it does work properly.
By the way my Axis box has the latest firmware and still doesn't work properly.
Hope this is helpful.
Here are a couple of photos of what I ended up making
As you can see I used the cables supplied with the Axxess box and also used the original cables that plug into the factory stereo to plug into the circuit board sockets. ( These you can't see in the photos )