Scan Tool Does Not Communicate With SDM

Circuit Description
The data link connector (DLC) is the provision for communicating with the Inflatable Restraint Sensing and Diagnostic Module (SDM) and other Class 2 modules that are on the same data line. The DLC is located under the LH side of the instrument panel. The DLC supplies B+ and ground to the scan tool. The scan tool communicates with the SDM and other Class 2 modules that are on the data line.The scan tool is connected to the DLC in order to perform the following functions:
^ Read the data list.
^ Read diagnostic trouble codes (DTCs).
^ Clear DTCs.

Diagnostic Aids
The loss of serial data communication between the SDM and the instrument cluster will cause the AIR BAG warning lamp to come ON solid. Refer to [1][2]Data Link Communications System Check in Data Link Communications.

Test Description
2. This test checks for proper operation of the scan tool.
3. This test checks for scan tool communication with the PCM.
4. This test checks for a blown AIR BAG Fuse.
6. This test determines whether there is a short to ground in circuit 1139 or if the SDM is malfunctioning.
9. This test checks for an open or high resistance condition in circuit 1139.
11. This test determines whether there is an open or high resistance in circuit 1128 or if the SDM is malfunctioning.