Data Link Connector
The serial data line is the means by which microprocessor-controlled modules in vehicle communicate with each other. Each module is assigned a specific recognition code known as source ID. This code is used to identify which module is communicating on serial data circuit. When a message is sent out on serial data circuit, the recognition code will identify which particular module sent the message. These messages contain specific information, or commands, modules require to function properly. When a module receives a message it also "learns" the source ID of module that sent it. This source ID is used to determine which module actually sent message and for State Of Health (SOH) monitoring. When ignition switch is in RUN position, each module communicating on class 2 serial data circuit sends a SOH message every 2 seconds to ensure that module is operating properly. When a module stops communicating on class 2 serial data circuit, for example if module loses power or ground, the SOH message it normally sends on data line every 2 seconds disappears. Other modules on class 2 serial data circuit, which expect to receive that SOH message, detect its absence. Modules receiving source ID then set an internal DTC associated with loss of SOH of non-communicating module. DTC is unique to the module which is not communicating. For example, when Body Control Module (BCM) SOH message disappears, several modules set DTC U1064. Note that a loss of serial data DTC does not normally represent a failure of module that set it.
The Data Link Connector (DLC) allows a scan tool to communicate with class 2 serial data circuit. DLC is a standardized 16-pin connector located below left side of instrument panel. Both connector design and location are dictated by industry wide agreements. All DLCs are required to provide a power supply, hot at all times, to terminal 16. This circuit is used to power the scan tool. All DLCs supply a power ground at terminal 4 and a signal ground at terminal 5. The class 2 serial data circuit is provided at terminal 2 of DLC. Once scan tool is connected to class 2 serial data circuit through DLC, scan tool can be used to monitor each module for diagnostic purposes and to check for DTCs.
The class 2 serial data circuit allows these modules to communicate data with each other:
- Body Control Module (BCM).
- Driver Information Center (DIC).
- Electronic Brake Control Module (EBCM).
- Heads Up Display Module (HUD).
- Instrument Panel Cluster (IPC).
- PASS-Key® III (PK3).
- Powertrain Control Module (PCM).
- Radio.
- Inflatable Restraint Sensing and Diagnostic Module (SDM).
- Devices on auxiliary power drop connector.