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. 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 logic state of 0 on the bus. When the bus is pulled low, 0 volts, it is translated as a logic state of 1. To wake the control modules connected to the low speed GMLAN serial data bus, a wake up signal is sent out over the bus. Modules connected to the low speed GMLAN bus can be part of a virtual network as described in the other GMLAN circuit descriptions above. The modules on the low speed GMLAN serial data bus are connected to the bus using several splice or "star" connectors separating groups of modules. The following lists state the splices and modules connected to the low speed serial data circuits:
I/P Splice
- Data link connector (DLC), connected only to the instrument panel (I/P) splice
- Amplifier (Amp)
- Rear seat audio (RSA)
- Vehicle communication interface module (VCIM)
- Digital radio receiver (DRR)
- Inside rearview mirror module (ISRVM), connected through the mid I/P fuse block
- Instrument panel cluster (IPC)
- Body control module (BCM)
- Theft deterrent module (TDM)
- Heater ventilation and air conditioning (HVAC)
- Radio
- Driver door switch (DDS), connected through the left I/P fuse block
- Passenger door switch (PDS), connected through the right I/P fuse block
Body Splice
- Articulating running board module (ARBM)
- Ultrasonic park assist (UPA)
- Memory seat module (MSM)
- Liftgate module (LGM)
- Passenger presence system (PPS)
- Inflatable restraint vehicle rollover sensor (ROS)
- Inflatable restraint sensing and diagnostic module (SDM)