DTC U1300: Class 2 Serial Data Link Low: Description
WARNING: This page is about a different car, the 2001 GMC Safari and 2001 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
Modules connected to class 2 serial data circuit monitor for serial data communications during vehicle operation. A State Of Health (SOH) message is communicated from each module to all other modules every 2 seconds. If a module detects low voltage and no SOH messages along class 2 serial data line for approximately 3 seconds, DTC U1300 will set. When DTC U1300 is set, no additional communication DTCs (communication DTCs begin with "U") can set.