If it's a P25 system, all you need are the control channels. The system and scanner do the rest. If you got to ID SCANNING, it's trunking correctly. Changing the System Options and setting ID SEARCH to ON will result in ID SEARCHING and you should hear any TGs on the system that are NOT AVOIDED or disabled and whose SERVICE TYPES are enabled if you have the TGs programmed in. Check these three possibilities. (enable all the SERVICE TYPES, de-program or enable all the Quick Keys, and make sure nothing is in the AVOID list).