Circuit/System Description

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The serial data gateway (SDG) module translates serial data messages between the high speed GMLAN serial data bus, the low speed GMLAN serial data bus, and the high speed hybrid GMLAN serial data bus. Messages between the drive motor generator battery control module and the other hybrid system control modules must pass thru the SDG module. The wake up circuit sends a voltage from the SDG module to the drive motor generator battery control module to initiate certain module functions. DTC U1813 is set by the drive motor generator battery control module, but is stored in and reported by the hybrid powertrain control module (HPCM).