Data Link References

This table identifies which serial data link that a particular module uses for in-vehicle data transmission. Some modules may use more than one data link to communicate. Some modules may have multiple communication circuits passing through them without actively communicating on that data link. This table is used to assist in correcting a communication malfunction. The body control module (BCM) emulates some devices that are on high speed GMLAN serial data circuit to the modules on class 2 serial data circuit. The BCM transmits multiple Node Alive messages using source IDs that correspond to each of those high speed GMLAN nodes. This is in addition to the BCM behaving itself as a real node. For the description and operation of these serial data communication circuits refer to Data Link Communications Description and Operation .

IMPORTANT: If the scan tool does not communicate with the vehicle the class two serial data bus must be diagnosed, repaired and functional first in order to prevent misdiagnosis.

Control Module	Data Link Type	Diagnostic Procedure
Schematic Reference: Data Communication Schematics
Adaptive Cruise Control (ACC) Module - XLR only	High Speed GMLAN	Scan Tool Does Not Communicate with High Speed GMLAN Device
Adaptive Forward Lighting System (AFS) - XLR only	High Speed GMLAN	Scan Tool Does Not Communicate with High Speed GMLAN Device
Audio Amplifier (Amp)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Body Control Module (BCM)	High Speed GMLAN Class 2	Scan Tool Does Not Communicate with High Speed GMLAN Device Scan Tool Does Not Communicate with Class 2 Device
Digital Radio Receiver (DRR)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Driver Door Module (DDM)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Driver Door Switch (DDS)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Driver Position Module (Memory Seat Module)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Electronic Brake Control Module (EBCM)	High Speed GMLAN	Scan Tool Does Not Communicate with High Speed GMLAN Device
Electronic Suspension Control (ESC or MRRTD) Module	High Speed GMLAN	Scan Tool Does Not Communicate with High Speed GMLAN Device
Engine Control Module (ECM)	High Speed GMLAN	Scan Tool Does Not Communicate with High Speed GMLAN Device
Exhaust Flow Module (EFM, w/ Z06 only)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Folding Top Controller (FTC, w/ convertible top only)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Fuel System Control Module (FSCM, w/ LS9 engine only)	High Speed GMLAN	Scan Tool Does Not Communicate with High Speed GMLAN Device
Head Up Display (HUD)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
HVAC Control Module	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Inflatable Restraint Sensing and Diagnostic Module (SDM)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Instrument Panel Cluster (IPC)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Passenger Door Module (PDM)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Radio	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Remote Control Door Lock Receiver (RCDLR)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Steering Column Lock Control Module (Manual Trans or Europe or Japan markets only)	Class 2	Scan Tool Does Not Communicate with Class 2 Device
Transmission Control Module (TCM)	High Speed GMLAN	Scan Tool Does Not Communicate with High Speed GMLAN Device
Vehicle Communication Interface Module (OnStar® VCIM)	High Speed GMLAN - pass through only Class 2	Scan Tool Does Not Communicate with Class 2 Device