Class 2 Serial Data

The Class 2 serial data circuit allows the control modules to communicate with each other. The modules send a series of digital signals pulsed from high to low voltage (approximately 7 volts to 0 volts). These signals are sent in variable pulse widths of one or two bits. A string of these bits creates a message that is sent in a prioritized data packet. This allows more than one module to send messages at the same time without overloading the serial data line. When the key is ON, each module sends a State of Health message to the other control modules using the class 2 serial data line. This ensures that the modules are working properly. When the module stops communicating, a loss of the state of health message occurs. The control modules that expect to receive the message detect the loss, and will set a loss of the state of health Diagnostic Trouble Code (DTC).