Circuit Description

Regulations and agreements among the automobile manufacturers have resulted in the data link connector (DLC). This connector must be used for the scan tool and programming access to all communications systems used for those purposes on the vehicle. The connector must have the following:

• A 16-pin connector configuration to which all scan tools connect
• Scan tool battery power always available at pin 16
• Scan tool ground always available at pin 4
• A clean signal ground always available at pin 5

The rest of the pins are available for serial data communications to the vehicle system.

The serial data circuits are the means by which the microprocessor-controlled modules in the vehicle communicate with each other and the scan tool. There are 3 different types of protocols on this vehicle:

• The Universal Asynchronous Receiver Transmitter (UART)
• Keyword 2000 Data line
• Key word 82 Data line

The scan tool accesses the following module data lines:

• The electronic brake control module (EBCM) (Keyword 2000)
• The engine control module (ECM) (Keyword 2000)
• The transmission control module (TCM) (Keyword 2000)
• The inflatable restraint sensing and diagnostic module (SDM) (UART)
• The intelligent switching unit (ISU) (Keyword 2000)
• The speed sensitive power steering (SSPS) module (Keyword 82)