Chevy Impala LT New key fob programming

Ashley1412

I was just given a 09 impala LT but it didn' come with the key fob so I bought a set of 2 online. Just received them today and when I went to program them 2 things happened. Firstly, I can only have one of them programmed at a time? I programmed both several times but only one would work at a time afterward. The one that was programmed second. Secondly, only the lock and unlock buttons work. The trunk button will not work. The instructions I looked up online simply says to hold down the lock and unlock buttons together until the car beeps. They say nothing about having to program the trunk button separately. The only time the fob trunk button works is while the key reset mode is in use after programming the fob but the second it gets turned off the button will no longer work. Are these simply crappy fobs that I bought or am I doing something wrong?

thecardoc3

They are probably clone keys (fobs). To perform a command the key and the car talk back and forth. First the key sends a signal and then the car responds with a question that the key has to answer. This get's synchronized during the training. Once the car learns a key ID and the fob learns the question you are ready to go. The problem with a clone is that it broadcasts the same key ID and since the module has already trained the first key with one question and it trains the second fob with a different question the first fob stops working.
While this is a Ford the technology is similar. The green is the car talking to the key and the red is the response. This car failed to learn the keys because they were clones. Sourcing two original keys was necessary for the initial programming. You don't have to be able to read the data to compare the two red captures, just look at the patterns and you can see that they are different.

Ashley1412

Ok so I can't have both of them programmed at the same time then? What about the trunk button not working?

thecardoc3

I would have to connect a scan tool to see if there is a blocking condition preventing operation. Then I would have to watch data in the receiving module and find out if the BCM is being sent the request and attempting to make the command.