Scan Tool Does Not Communicate With Class 2 Device

CIRCUIT DESCRIPTION
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 DLC allows communication with the modules for diagnostic purposes.

Diagnostic trouble codes (DTCs) may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

DIAGNOSTIC AIDS
The BCM detects the ignition switch position and sends the appropriate power mode message to the other modules. The BCM must be connected to the class 2 serial data circuit for any other module to communicate with the scan tool.

TEST DESCRIPTION

Steps 1-2:

Steps 3-11:

Steps 12-17:

Steps 18-24:

Steps 25-31:

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. The following modules communicate on the class 2 serial data circuit:
^ PCM
^ EBCM
^ SDM
^ IPC
^ BCM
^ HVAC Control Module
^ VIU.
3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition.
^ U1300
^ U1301
6. A State of Health DTC for a specific module with a history status may be present along with a U1000 or U1255 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.
9. A poor connection at the star connector terminal for the DLC would cause this condition but will not set a DTC.
10. An open in the class 2 serial data circuit between the DLC and star connector will prevent the scan tool from communicating with any module. This condition will not set a DTC.
11. The BCM detects the ignition switch position and sends the appropriate power mode message to the other modules. The BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the BCM class 2 serial data circuit.
13. This test isolates the PCM class 2 serial data circuit.
15. This test isolates the EBCM class 2 serial data circuit.
17. This test isolates the SDM class 2 serial data circuit.
19. This test isolates the IPC class 2 serial data circuit.
21. This test isolates the HVAC Control Module class 2 serial data circuit.
23. This test isolates the VIU class 2 serial data circuit.
26. The communication malfunction may have prevented diagnosis of the customer complaint.
27. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.