Hi there new member to forum .I recently bought a mazda3 sport 55 reg.I have 2 questions . One of the keys does not start the car ,it opens and closes doors etc but when inserted in ignition barrel it does not remove the key sign on the dash.Suspect problem with coding in key anyone had this problem that can advise.
Also fuel consumption it seems to drink the fuel only getting about 140 miles for
£20

 

Are the 3's over there equipped with the immobilizer system and require transponder keys? When you put the key in the ignition does the key light (car with key symbol on it) flash very quickly? If so then what the car is telling you is you've inserted a key who's transponder chip is not registered with the ECU.

Assuming that your key programming is the same for US versions (and I can't imagine it's different) then you can only program in your own key if you have two working keys already. If you only have one working key then the dealer needs to plug into your computer, clear out the existing key codes, and reprogram in the "new" ones.

You said you just bought this car..... did you buy it new? If so then I'd demand (nicely, no need to get their back's up) that they program in your second key for free as obviously anything they give you should work. Beyond that I'd suggest getting a third key as a backup, that way if you ever lose one of the three keys you can just buy another and program it in yourself (invalidating the lost key), vs. being back in the same predicament that you are in now.

The 3's computer will support 8 transponder keys.