Low Speed GMLAN Circuit Description

WARNING: This page is about a different car, the 2010 GMC Terrain and 2010 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.

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 low speed GMLAN is up to 83.33 Kb/s. Under normal vehicle operating conditions, the speed of the bus is 33.33 Kb/s. This protocol produces a simple pulse train sent out over the low speed GMLAN serial data bus. When a module pulls the bus high, 5 volts, this creates a dominant logic state or 0 on the bus. When the bus is pulled low, 0 volts, it is translated as a recessive logic state or 1. To wake the control modules connected to the low speed GMLAN serial data bus, a high voltage wake up pulse is sent out over the bus, the voltage level of the pulse is +10 volts. Modules connected to the low speed GMLAN bus can be part of a virtual network as described in the previous paragraph. The modules on the low speed GMLAN serial data bus are connected to the bus in a parallel configuration.