LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 2009 >> Escalade EXT >> Repair and Diagnosis >> Engine Performance >> System >> Data Communication System >> Diagnostic Information and Procedures >> DTC U209D >> Circuit/System Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Circuit/System Description

Modules connected to the LAN 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 also, 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.

2 wake up signal circuits (5986, 5985) are energized by the body control module (BCM) to activate multiple modules including the drive motor generator battery control module (BECM) when serial data is required. Wake up signal circuit (968) is energized by the serial data gateway module (SDGM) to activate the BECM immediately after the BCM energizes circuit 5986 and 5985. The BECM compares the status of both wake up circuits.