Circuit Description
The inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) performs tests to diagnose critical malfunctions within itself when the ignition switch is turned ON. The SDM monitors the six firing loops to detect leakage currents to ground and system voltage in the frontal and side air bag inflator module and seat belt pretensioner circuits. The deployment loop resistances are measured to ensure they are within their respective normal resistance ranges. Upon passing these tests, and if the energy reserve is charged up, the firing transistors are tested. The SDM then goes into Continuous Monitoring mode. The SDM service wait time is 1 minute. Refer to On-Vehicle Service for enable/disable procedures.
Conditions for Setting the DTC
| • | The ignition is within normal operating voltage range. |
| • | The measured leakage currents to ground in the driver Side Impact Sensor (SIS) loop are above a specified value caused by a short circuit from the driver Side Impact Sensor (SIS) loop to ground. |
The driver Side Impact Sensor (SIS) loop consists of the following components:
| • | The inflatable restraint Side Impact Sensor (LH) . |
| • | The harness wiring of CKT B41. |
| • | The harness wiring of CKT B42. |
| • | The harness wiring of CKT XB42. |
| • | The connector terminal contact. |
DTC 74 will set once one of these conditions is met. This test is run during the SDM Turn-ON tests.
Action Taken When the DTC Sets
| • | The SDM sets a Diagnostic Trouble Code. |
| • | The SDM turns ON the AIR BAG warning lamp. |
Conditions for Clearing the DTC
Current and History DTC codes must be cleared using a scan tool Clear DTC Information command. If the circuit fault has been successfully repaired and the conditions which caused the Current DTC 74 to set are no longer existing, History DTC 74 will set. History DTC 74 may be cleared using the scan tool.
Diagnostic Aids
An inflatable restraint driver Side Impact Sensor (SIS) circuit short-to-ground can cause an intermittent condition. Inspect CKTs B41, B42 and XB42 carefully for cutting and/or chafing. A careful inspection of the circuits and components indicated on the DTC 74 Table is essential to make sure that the replacement SDM will not be damaged.
When measurements are requested in this table, use J 39200 Digital Multimeter with the correct terminal adapter from J 35616 Connector Test Adapter Kit. When a check for proper connection is requested, refer to Intermittents and Poor Connections . When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair .
Test Description
The following numbers refer to the step numbers on the diagnostic table:
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This test determines whether the malfunction is a short to ground condition in CKT B42 in the LH door electrical harness.
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This test determines whether the malfunction is a short to ground condition in CKT XB42 in the LH door electrical harness.
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This test determines whether the malfunction is a short to ground condition in CKT B41.
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This test determines whether the malfunction is a short to ground condition in CKT XB42 between the LH side door electrical connector and the SDM harness connnector.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System Check performed? | -- | ||
2 |
Are the terminals damaged or corroded? | -- | ||
3 | Replace the LH door electrical harness. Is the replacement complete? | -- | -- | |
4 | Check for proper connection of terminal 39 and terminal 40 on the harness side of the LH door electrical connector C500. Are the terminals damaged and/or corroded? | -- | ||
5 | Check for proper connection of terminal 39 and terminal 40 on the harness side of the LH door electrical connector C500. Are the terminals damaged and/or corroded? | -- | ||
6 | Replace the body harness Is the replacement complete? | -- | -- | |
Is the resistance reading less than the specified value? | OL | |||
8 | Repair the short to ground in CKT B42 between the LH door side impact sensor 2-way connector terminal 1 and terminal 40 of the LH door electrical connector C500. Is the repair complete? | -- | -- | |
Use the J 39200 to measure the resistance from the LH side impact sensor 2-way connector terminal 2 to a known good ground. Is the resistance reading less than the specified value? | OL | |||
10 | Repair the short to ground condition in CKT XB42 between the LH door side impact sensor 2-way connector terminal 2 and terminal 39 of the LH door electrical connector C500. Is the repair complete? | -- | -- | |
11 |
Are the terminals damaged or corroded? | -- | ||
12 | Repair the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) harness connector. Is the repair complete? | -- | -- | |
13 | Check for proper connection at terminal 41 and terminal 42. Are the terminals damaged or corroded? | -- | ||
14 | Check for proper connection at terminal 41 and terminal 42. Are the terminals damaged or corroded? | -- | ||
15 | Replace the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement . Is the replacement complete? | -- | -- | |
Use the J 39200 to measure the resistance from the SDM harness connector terminal 41 to terminal 7 (ground). Is the resistance reading less than the specified value? | OL | |||
17 | Repair the short to ground condition in CKT B41 between the body harness side of the LH door electrical connector C500 and SDM harness connector. Is the repair complete? | -- | -- | |
Use the J 39200 to measure the resistance from the SDM harness connector terminal 42 to terminal 7 (ground). Is the resistance reading less than the specified value? | OL | Go to Integrity Check | ||
19 | Repair the short to ground condition in CKT XB42 between the body harness side of the LH door electrical connector C500 and SDM harness connector. Is the repair complete? | -- | -- | |
20 | Reconnect all the SIR components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | ||
21 | Clear all the SIR DTCs. Have all the DTCs been cleared? | -- | -- |
