Low Speed GMLAN Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the low speed GMLAN serial data circuit. The serial data is transmitted over a single wire to the appropriate control modules. The transmission speed for GMLAN low speed is up to 83.33 Kbps. This high speed is used for programming purposes only. Under normal vehicle operating conditions the speed of the bus is 33.33 Kbps. This protocol produces a simple pulse train sent out over the low speed GMLAN serial data bus. To wake up the control modules connected to the low speed GMLAN serial data bus, a wake-up pulse of 10 volts is sent out over the bus.