Class 2 Serial Data Line
Modules communicate along one common Purple wire referred to as class 2 serial data line. Serial data line is used to communicate information between systems. Each system on the serial data line is assigned its own unique identification number, which is used to identify itself to other modules or systems. Class 2 serial data line also allows communication with scan tool through Data Link Connector (DLC). See Fig 1. Modules communicating along class 2 serial data line are as follow:
- Cellular Telephone Module
- Dash Integration Module (DIM)
- Driver's Door Module (DDM)
- Driver's Door Switch Assembly (DDSA)
- Electronic Brake Control Module (EBCM)
- Electronic Suspension Control Module (ESC)
- Front Passenger's Door Module (FPDM)
- Heater Ventilation Air Conditioning (HVAC) Control Module - Auxiliary
- Inflatable Restraint Sensing And Diagnostic Module (SDM)
- Instrument Panel Cluster (IPC)
- Instrument Panel Integration Module (IPM)
- Left Middle Door Module (LMDM) with RPO code V4U
- Left Rear Door Module (LRDM)
- Memory Seat Module (MSM) with RPO code A45
- Navigation Data Processor (with RPO code UY4)
- Navigation Display Head (with RPO code UY4)
- Powertrain Control Module (PCM)
- Radio
- Radio Amplifier
- Rear Integration Module (RIM)
- Remote Control Door Lock Receiver (RCDLR)
- Right Front Window Switch (with RPO code B05)
- Right Middle Door Module (RMDM) with RPO code V4U
- Right Rear Door Module (RRDM)
- Steering Column Module (with RPO code N37)
- Theft Deterrent Module
- Vehicle Interface Unit (On-Star(R))
Systems periodically send a State of Health (SOH) message to other systems. If those systems fail to send an SOH message back, a corresponding DTC will be set. Also, any system that cannot communicate properly will set a DTC.