Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.
The numbers below refer to the step numbers on the diagnostic table.
A current DTC U1305 may be retrieved only from the body control module (BCM).
A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on the class 2 serial data circuit. The BCM is diagnosed only through GMLAN serial data circuit.
• | Body control module (BCM) |
• | Communication interface module (OnStar®) |
• | Digital radio receiver (DRR) |
• | Driver door module (DDM) |
• | Driver door switch (DDS) |
• | Driver position module (DPM) |
• | Folding top controller (FTC) |
• | Head up display (HUD) |
• | HVAC control module |
• | Inflatable restraint sensing and diagnostic module (SDM) |
• | Instrument panel cluster (IPC) |
• | Passenger door module (PDM) |
• | Radio |
• | Remote control door lock receiver (RCDLR) |
• | Steering column lock control module (SCLCM) |
Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
A poor connection at splice pack SP205 will cause this condition but will not set a DTC.
An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module on the class 2 network. This condition will not set a DTC.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Data Communication Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Are the DTCs U1300, U1301 or U1305 retrieved from any module? | Go to Step 3 | ||
Did the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 4 | Go to Step 7 | |
4 | Did you record any DTCs in the range of U1000 to U1255? | Go to Step 5 | Go to Step 6 |
5 | Did you record any DTCs in the range of U1001 to U1254? | Go to DTC U1001-U1254 | Go to DTC U1000 and U1255 |
6 | Diagnose the non-communicating module by using the DTC U1001-U2154 procedure for the module which is not communicating. Refer to DTC U1001-U1254 . Did you complete the action? | -- | |
Did you find and correct the condition? | Go to Step 8 | ||
8 | Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 9 | |
Did you find and correct the condition? | Go to Step 10 | ||
Repair the class 2 serial data circuit between the DLC and the splice pack SP205 for an open. Refer to Circuit Testing and Wiring Repairs . Did you complete the action? | System OK | -- |