Sensing and Diagnostic Module (SDM) Integrity Check

The following diagnostic chart must be used when all circuitry outside the sensing and diagnostic module (SDM) has been found to operate properly, as indicated by following the appropriate diagnostic trouble code (DTC) chart. This chart verifies the need for SDM replacement.

Circuit Description
When the SDM recognizes Ignition 1 voltage greater than 8.2 volts at terminal 10 of the SDM, the AIRBAG indicator flashes seven times to verify operation. The SDM then performs turn-on tests followed by resistance measurement tests and continuous monitoring tests. When a malfunction is detected, the SDM sets a current DTC and illuminates the AIRBAG indicator. When the malfunction is no longer detected and/or the ignition switch is cycled, the SDM will clear current DTCs and move them to a historic file, except for DTCs 18, 24, 51, 53, and sometimes 71. DTCs 18, 24, 51, and 53 will not clear using a scan tool because these codes require replacement of the SDM. The SDM must be replaced only after the malfunction that set the DTC has been repaired.

Test Description
The numbers below refer to steps on the diagnostic table.

1. This test confirms a current malfunction. If no current malfunction is occurring, refer to Diagnostic Aids for the appropriate DTC. The SDM should not be replaced for a historic DTC except when directed.
2. This test checks for a malfunction introduced into the SIR system during the diagnostic process. It is extremely unlikely that a malfunctioning SDM would cause a new malfunction to occur during the diagnostic process.
4. Refer to the cautions below.

Steps 1 - 4:

Sensing and Diagnostic Module (SDM) Integrity Check

CAUTION: The sensing and diagnostic module (SDM) can maintain sufficient voltage to deploy the airbags for 10 minutes after the ignition is OFF and the fuse has been removed. If the airbags are not disconnected, do not begin service until 10 minutes have passed after disconnecting power to the SDM. Otherwise, injury could result.

CAUTION: During service procedures, be very careful when handling the SDM. Never strike or jar the SDM. Never power the supplemental inflatable restraints (SIR) system when the SDM is not rigidly attached to the vehicle. All SDM mounting bolts must be carefully tightened, and the SDM arrow must be pointing toward the front of the vehicle to ensure proper operation of the SIR system. The SDM could be activated if it Is powered when it is not rigidly attached to the vehicle, resulting in unexpected deployment and possible injury.