J1850-10.4J1850-10.4 - GM Class-2The SAE J1850.10.4 standard refers to the GM Class-2 communication protocol. This protocol has beenused by General Motors since 1996.With Class 2 data, each bit of information can have one of two lengths, long (128 us) or short (64 us). This isreferred to as Variable Pulse Width (VPW). This allows the vehicle wiring to be reduced by the transmissionand reception of the multiple signals over a single wire. The messages which are carried on Class 2 datastreams are also prioritized. In other words, if two messages attempt to establish communications on thedata line at the same time, only the message with the higher priority will continue. The device with thelower priority message must wait.The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The serialdata line is the means by which the microprocessor-controlled modules that are connected to it
This is the end of the preview.
access the rest of the document.