TC and CG Terminal Circuit: Description
WARNING: This page is about a different car, the 2007 Toyota Tacoma. However, it is still accessible from the selected car via links, so may be relevant.
The DLC3 circuit enables reading of Diagnostic Trouble Codes (DTCs) with no intelligent testers by connecting terminals TC and CG of the DLC3 connector.
Stored DTCs are displayed in blinking patterns of the CRUISE MAIN indicator light located on the combination meter.