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Circuit/System Description
The internal fault detection is handled inside the control module. No external circuits are involved.
Some control modules must be configured with serial numbers, vehicle options, or other information. If a control module was not properly configured after installation, that module may set DTC B1001.
The internal fault detection is handled inside the control module. No external circuits are involved.
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 body control module (BCM) activates the serial data communication enable and the accessory wakeup serial data circuits by applying voltage when the ignition key is in ACC, ON or START. Only the modules using high speed GMLAN serial data are connected to the enable or wakeup circuits. To determine which modules are activated using the enable or wakeup circuits refer to Data Communication Schematics .
The serial data circuits are serial data buses are used to communicate information between the control modules. The serial data circuits also connect directly to the data link connector (DLC).
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 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.
The body control module (BCM) activates the high speed GMLAN serial data wake up and the accessory wake up serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The high speed GMLAN serial data wake up circuit wakes up the electronic brake control module (EBCM) for bus communication and the accessory wake up serial data circuit wakes up the engine control module (ECM) and transmission control module (TCM).
The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following
- Scan tool B+ voltage at terminal 16
- Scan tool ground at terminal 4
- Common ground at terminal 5
Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The high speed GMLAN serial data circuits must be operational for the vehicle to start due to steering column control module (SCCM) and engine control module (ECM) communications. The vehicle theft deterrent (VTD) module and ECM exchange information using the SCCM as the gateway module allowing communication between the high and low speed serial data buses. The low speed GMLAN serial data circuit must also be operational for vehicle starting. The high speed GMLAN serial data bus uses two 120-ohm terminating resistors that are in parallel with the high speed GMLAN (+) and (-) circuits. One of the resistors is in the rear cargo area and the other is internal to the ECM.
Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The high speed GMLAN serial data circuits must be operational for the vehicle to start due to steering column control module (SCCM) and engine control module (ECM) communications. The vehicle theft deterrent (VTD) module and ECM exchange information using the BCM as the gateway module allowing communication between the high and low speed serial data buses. The low speed GMLAN serial data circuit must also be operational for vehicle starting. The high speed GMLAN serial data bus uses two 120-ohm terminating resistors that are in parallel with the high speed GMLAN (+) and (-) circuits. One of the resistors is in the rear cargo area and the other is internal to the ECM.
Modules connected to the low speed GMLAN serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The low speed GMLAN serial data circuit must be operational for the vehicle to start so the vehicle theft deterrent (VTD) module and Steering Column Control Module (SCCM) can communicate.
Local Interconnect Network (LIN) Description
The driver door module (DDM) and the front passenger door module (FPDM) communicate with window motors on the local interconnect network bus 1 and the local interconnect network bus 2 circuits respectively. The DDM LIN buss is connected to all window motors on its side of the vehicle, while the FPDM LIN buss is connected to the other window motors. Communication on this network is only between the door modules and the window motors. The window motors are in effect modules. The window motor modules do not communicate on any other data buss; therefore the door modules, which also communicate on the low speed GMLAN serial data buss will perform all communication with each other, the motors, the SCCM (gateway) and the scan tool including setting LIN buss DTCs.