Circuit Description
When the ignition switch is first turned to RUN, Ignition Positive Voltage is applied to the instrument cluster. The instrument cluster responds by flashing the AIR BAG warning lamp seven times to verify operation. When the inflatable restraint sensing and diagnostic module (SDM) recognizes Ignition Positive Voltage, applied to terminal 3, is greater than 8.2 volts, the SDM performs POWER-ON tests followed by the RESISTANCE MEASUREMENT test and the CONTINUOUS MONITORING tests. Upon detection of a malfunction, the SDM sets a current Diagnostic Trouble Code (DTC) commands the instrument cluster to illuminate the AIR BAG warning lamp. The SDM will clear current DTCs and preserve them in a history file when:
| • | The malfunction is no longer detected. |
| • | The ignition switch is cycled. |
This does not include the following DTCs:
| • | DTC B1151 |
| • | DTC B1152 |
| • | DTC B1153 |
| • | DTC B1171 |
DTCs B1151 and B1153 can only be cleared using a scan tool CLEAR CODES command. DTC B1152 will clear from current DTCs so that you can diagnose the vehicle but will latch as a history DTC. DTC B1171 may not clear after a CLEAR CODES command.
Important: Repair the malfunction that set the DTC before you replace the SDM.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This test confirms a circuit malfunction. If no current malfunction is occurring (history DTC set), refer to the diagnostic aids for the appropriate DTC table as indicated through the scan tool. Do not replace the inflatable restraint Sensing and Diagnostic Module (SDM) for a history DTC other than DTC B1171.
-
This test checks for a malfunction introduced into the SIR system during the diagnostic process. It is unlikely that a malfunctioning SDM would cause a new malfunction to occur during this process.
-
When you have found all circuitry outside the SDM to operate properly, as indicated by the appropriate diagnostic table, replace the SDM.
This table assumes that the SIR Diagnostic System Check and either a symptom table or a Diagnostic Trouble Code table diagnosis has been performed. When all circuitry outside the inflatable restraint Sensing and Diagnostic Module (SDM) has been found to operate properly, as indicated by the appropriate diagnostic table, and the symptom or DTC remains current, the following diagnostic procedures must be performed to verify the need for SDM replacement.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Were you sent here from a symptom table or a Diagnostic Trouble Code (DTC) table? | -- | Go to Step 2 | |
Does the AIR BAG warning lamp flash seven times then go OFF? | -- | Go to Step 7 | Go to Step 3 | |
Using the scan tool, request the SIR DTC display. Is the same symptom or DTC occurring as when the SIR Diagnostic System Check was first performed? | -- | Go to Step 4 | ||
Does the AIR BAG warning lamp flash seven times then go OFF? | -- | System OK | Go to Step 5 | |
5 |
Has the SDM been replaced? | -- | Go to Step 6 | -- |
6 | Reconnect all the SIR system components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | -- | |
7 | Clear the SIR DTCs. Have the SIR DTCs been cleared? | -- | -- |
