For 1990-2009 cars

The microprocessor-controlled modules in the vehicle communicate with each other through the serial data lines. This vehicle uses 2 serial data lines as follows:

• | The UART serial data line

• | The Class 2 serial data line

### UART Serial Data Line

UART-based communication systems have a master of the serial data line and remote transceivers. The master controls the message traffic on the serial data line by polling all of the remotes (control modules). The master then waits for the proper response.

The control module on the UART data line is the sensing and diagnostic module (SDM).

### Class 2 Data Line

Class 2 data is transmitted at a higher speed. The messages have a different configuration than UART data. While UART uses a master in order to control serial data line traffic, Class 2 uses the peer-to-peer method along with message arbitration in order to manage the data line traffic.

The control modules on the Class 2 data line include the following modules:

• | The powertrain control module (PCM)

• | The body control module (BCM)

• | The electronic brake control module (EBCM)