Circuit Description
When you first turn the ignition switch to the RUN position, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within the SDM. Upon passing these tests the following circuits are measured to ensure that they are within their respective normal voltage ranges:
| • | IGNITION 1 |
| • | 23 VLR |
| • | Deployment loop voltages |
Then the SDM proceeds to CONTINUOUS MONITORING. The SDM contains a resistor network connected to 5 volts, ground, and to the SDM front-end sensor signal terminal 9. The 1.0 K ohm resistor in the inflatable restraint front end discriminating sensor parallel to the normally open switch provides a parallel path to ground. This causes a specified percentage of voltage to appear at the SDM front-end sensor signal input. The SDM monitors this voltage to detect shorts to power or an open discriminating sensor.
Conditions for Setting the DTC
| • | The SDM is configured for an inflatable restraint front end discriminating sensor |
| • | The voltage at front-end sensor signal terminal 9 is more than 5.0 volts for 500 milliseconds. |
The CONTINUOUS MONITORING test inspects for this DTC. This test occurs when IGNITION 1 is within the normal operating voltage range.
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 DTC--The voltage at front-end sensor signal terminal 9 is less than 3.2 volts for 500 milliseconds. |
| • | History DTC |
| - | You issue a scan tool CLEAR CODES command |
| - | After 250 malfunction free ignition cycles have occurred |
Diagnostic Aids
A broken or chafed wire in the inflatable restraint front end discriminating sensor circuit may cause an intermittent condition. Inspect CKT 349 and CKT 1751 carefully for cut or chafed wires.
When measurements are requested in this table, use the J 39200 DMM with the correct terminal adapter from the J 35616 Connector Test Adapter Kit. When an inspection for proper connection is requested, refer to Testing for Electrical Intermittents in Wiring Systems. When a wire, connector or terminal repair is requested, use the J-38125 Terminal Repair Kit and refer to Wiring Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This test inspects for proper contact or corrosion of the yellow 2-way connector.
-
This test inspects for a malfunctioning discriminating sensor.
-
This test inspects for an open in CKT 1751.
-
This test isolates the open in CKT 1751 to one side of C114.
-
This test inspects for proper contact or corrosion of the inflatable restraint sensing and diagnostic module (SDM) connector.
-
This test inspects for an open in CKT 349.
-
This test isolates the open in CKT 349 to one side of C114.
-
This test inspects for a short to voltage in CKT 349.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System Check performed? | -- | Go to Step 2 | |
Are the terminals damaged or corroded? | -- | Go to Step 3 | Go to Step 5 | |
3 | Replace the sensor harness connector. Refer to Wiring Repair . Is the repair complete? | -- | Go to Step 4 | -- |
4 | Inspect for proper connection at the sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | Go to Step 6 | Go to Step 27 |
5 | Inspect for proper connection at the sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | Go to Step 6 | Go to Step 7 |
6 | Replace the inflatable restraint front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement . Is the repair complete? | -- | Go to Step 27 | -- |
Measure the resistance between the sensor connector terminals A and B. Is the resistance reading more than the specified value? | 1050 ohms | Go to Step 6 | Go to Step 8 | |
Measure the resistance from the sensor harness connector terminal B to ground. Is the resistance reading within the specified values? | 0-5 ohms | Go to Step 14 | Go to Step 9 | |
9 |
Is the terminal damaged or corroded? | -- | Go to Step 10 | Go to Step 11 |
10 | Replace C114. Refer to Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 27 | -- |
Measure the resistance between the sensor harness connector terminal B and C114 terminal B. Is the resistance reading within the specified values? | 0-5 ohms | Go to Step 12 | Go to Step 13 | |
12 | Repair an open condition in CKT 1751 between C114 and G202. Is the repair complete? | -- | Go to Step 27 | -- |
13 | Repair an open condition in CKT 1751 between C114 and the inflatable restraint front end discriminator sensor harness connector. Is the repair complete? | -- | Go to Step 27 | -- |
Is the connector damaged or corroded? | -- | Go to Step 15 | Go to Step 17 | |
15 | Replace the SDM harness connector. Refer to Wiring Repair . Is the repair complete? | -- | Go to Step 16 | -- |
16 | Inspect for proper connection at terminal 9 of the SDM. Is the terminal damaged or corroded? | -- | Go to Step 18 | Go to Step 27 |
17 | Inspect for proper connection at terminal 9 of the SDM. Is the terminal damaged or corroded? | -- | Go to Step 18 | Go to Step 19 |
18 | Replace the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Is the repair complete? | -- | Go to Step 27 | -- |
Measure the resistance between the sensor harness connector terminal A and the SDM harness connector terminal 9. Is the resistance reading within the specified values? | 0-5 ohms | Go to Step 25 | Go to Step 20 | |
20 |
Is the terminal damaged or corroded? | -- | Go to Step 21 | Go to Step 22 |
21 | Replace C114. Refer to Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 27 | -- |
Measure the resistance between the sensor harness connector terminal A and the C114 terminal A. Is the resistance reading within the specified values? | 0-5 ohms | Go to Step 23 | Go to Step 24 | |
23 | Repair an open condition or high resistance in CKT 349 between C114 and the SDM harness connector. Is the repair complete? | -- | Go to Step 27 | -- |
24 | Repair an open condition or high resistance in CKT 349 between C114 and the sensor harness connector. Is the repair complete? | -- | Go to Step 27 | -- |
Is the measured voltage equal to the specified value? | 0.0 V | Go to Step 26 | ||
26 |
Is the repair complete? | -- | Go to Step 27 | -- |
27 |
Have all the SIR components been reconnected and properly mounted? | -- | Go to Step 28 | -- |
28 | Clear all the SIR DTCs. Have all the SIR DTCs been cleared? | -- | -- |
