oh no! not another red key problem. the blue keys are both slaves. the red key is the master. that means the ecu is linked to the red key permanetly, and any blue key can be programmed into the ecu using the red key.
if your ecu has lost the blue key codes (key code light remains on when trying to start car, and engine wont start) and you dont have the red key you cant do much about it. the options are-
1. replace the ecu and all locks and keys with a set obtained from another car (£100 at scrapyards & breakers but its tricky finding a full set of keys and locks and ecu all from the same car, and making sure its the same engine as your car) fitting the whole lot is relatively easy, just a bit of a hassle.
2. go to
http://www.codeman.org/ and find out about getting the immobiliser disabled on your ecu. doesnt cost too much (£100-200), you simply post the ecu to them, it comes back ready to plug back into the car and away you go. both keys will work, but so will a screwdriver and force (no immobiliser!) so you'll need to consider installing some new security or take the risk. an aftermarket alarm/immob is cheap on ebay and easy to fit.
3. let fiat install a new ecu and provide a set of keys to fit your existing locks and work with the ecu. costing more than the car is worth.
and in future dont buy a fiat with a code system 1 immobiliser unless it has the red key (guess i dont need to tell you that now)
N.B. if your key code light isnt remaining on when you try to use a blue key then the problem isnt the key codes, its something else. dont take the diagnostic check as gospel. is the orange key code light staying on?