If your Tuner for a Toyota gets a T999 Update Agent Error it means that there is a connection issue with the update agent to our server.
Verify any Anti-Virus programs are off, or disabled and continue to retry the update until the server reconnects and allows an update. (If you are unsure how to disable your Anti-Virus program please refer to your user manual for that software.
If you continue to have this issue, please get in touch with us at techsupport@derivesystems.com or visit our chat option on our site, bullydog.com. Make sure you have access to a windows based pc, the device, and the vehicle when you do. Thanks.