DTCS Not Displayed Or Continuously Displayed: Description
WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
When Data Link Connector 3 (DLC3) terminals Tc and CG are connected together, air bag sensor assembly is set in Diagnostic Trouble Code (DTC) output mode. Diagnostic Trouble Code (DTC) is displayed by flashing of AIR BAG warning light.