Scan Tool Does Not Communicate With Class 2 Device

SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE

CIRCUIT DESCRIPTION
Each module connected to the class 2 serial data circuit monitors serial data communication 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.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC U1300 Class 2 Data Link Low
- DTC U1301 Class 2 Data Link High
- DTC U1305 Class 2 Data Link Low or High

DIAGNOSTIC AIDS
- The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.
- The power mode master (PMM) must be able to communicate with the other modules on the class 2 serial data bus in order for the Tech 2 to communicate with the other modules.
- The powertrain control module (PCM) on this vehicle has 3 junctions to the class 2 serial data bus.

TEST DESCRIPTION

Steps 1-9:

Steps 10-13:

Steps 14-19:

Steps 20-24:

Steps 25-34:

Steps 35-40:

The numbers below refer to the step numbers on the diagnostic table.
2. 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.
3. The DTC U1300 and U1301 may be retrieved with a history status. These DTCs are not the cause of the present condition.
6. A State of Health DTC with a history status may be present along with a DTC U1000 with a current status. This indicates that the malfunction occurred when the ignition was on.
7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
10. An open in the class 2 serial data circuit between the DLC and the body control module (BCM) will prevent the scan tool from communicating with any module. This condition will not set a DTC.
11. If communication can be established, the malfunction is not in the BCM or the wiring from the DLC to the BCM.
12. This test attempts to establish communication with the radio.
13. This test attempts to establish communication with the digital radio receiver (DRR).
14. This test attempts to establish communication with the OnStar vehicle communications interface module (VCIM).
15. This test attempts to establish communication with the PCM.
16. This test attempts to establish communication with the instrument panel cluster (IPC).
17. This test attempts to establish communication with the restraints sensing and diagnostic module (SDM).
18. This test attempts to establish communication with the electronic brake control module (EBCM).
19. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the BCM.
20. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the radio.
21. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit between the radio and the DRR module.
22. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit between the radio and the VCIM module.
23. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the PCM.
24. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the IPC.
25. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the SDM.
26. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the EBCM.
36. If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
38. The interruption of the class 2 serial data circuit may have prevented the diagnosis of the customer complaint.