Data Link Connector (DLC)

Data Link Connector (DLC):

DESCRIPTION
The provision for communicating with the control module is the Data Link Connector (DLC). It is usually located under the instrument panel. The DLC is used to connect to a scan tool. Some common uses of the scan tool are listed below:

- Identifying stored Diagnostic Trouble Codes (DTCs).
- Clearing DTCs
- Performing output control tests.
- Reading serial data.

Class II Serial Data
U.S. Federal regulations require that all automobile manufacturers establish a common communications system. General Motors utilizes the Class II communications system. Each bit of information can have one of two lengths: long or short. This allows vehicle wiring to be reduced by the transmission and reception of multiple signals over a single wire. The messages carried on Class II data streams are also prioritized. In other words, if two messages attempt to establish communications on the data line at the same time, only the message with higher priority will continue. The device with the lower priority message must wait. The most significant result of this regulation is that the regulation provides scan tool manufacturers with the capability of accessing data from any make or model vehicle sold in the United States.