Chart F DERM Cannot Communicate Through the Serial Data Line

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION
When the DERM recognizes "Ignition 1" voltage, applied to terminal "A9" and "A10," is in the normal operating voltage range, the "AIR BAG" warning lamp is flashed 7 times to verify operation. At this time the DERM performs "Turn-On" tests followed by "Continuous Monitoring" tests. When no malfunctions are detected the DERM proceeds to the "Initiator Assembly Resistance Test." When a malfunction is detected the DERM sets a current diagnostic trouble code and illuminates the "AIR BAG" warning lamp. The DERM will clear current diagnostic trouble codes and move them to a history file when the malfunction is no longer detected and/or the ignition switch is cycled, except for DTC 51. DTC 51 can only be cleared using a scan tool "Clear Codes" command.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test confirms proper operation of the scan tool.
2. An improper connection to the data link connector will prevent communications from being established.
3. This test checks for general "Serial Data" line malfunction.
4. This test checks for a short to ground in the "Serial Data" line.
5. This test checks for a short to B+ in the "Serial Data" line.
6. This test checks for an open in the "Serial Data" line.
7. This test determines whether the malfunction is due to an open in the "Serial Data" line or the DERM.