Cause code redefine

I have gsm-sip gateway equipment that return to asterisk cause 16 (normal clear) & connection time 0, when call was not connected(bcause gsm network problems or IVR answer).
Could some point me on configuration or sources hack for how to redefine cause 16 to another, when connection time is 0 ?

Thanks in advance.

This would best to be asked on the IRC channel. Probably the #asterisk-dev channel.