Circuit/System Description

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

The serial data circuit is the means by which the devices in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the X84 Data Link Connector (DLC), the scan tool can be used to monitor each device for diagnostic purposes and to check for Diagnostic Trouble Codes (DTC). Each device communicating on the serial data circuit sends data to each other. When a device stops communicating on the serial data circuit, for example if the device loses power or ground, the data it normally sends on the serial data circuit disappears. Other devices on the serial data circuit, which expect to receive that data, detect its absence; those devices in turn set a DTC associated with the loss of data of the non-communicating device. The DTC is unique to the device which is not communicating and one or more devices may set the same exact code. A loss of serial data communications DTC does not represent a failure of the devices that contain the stored code.