Circuit Description
When you first turn the ignition switch to the RUN position, the supplemental restraint Sensing and Diagnostic Module (SDM) performs tests to diagnose critical malfunctions within itself. Next the SDM measures IGNITION 1, 23 VLR and the deployment loop voltages to make sure they are within their respective normal voltage ranges. 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 SDM monitors two front end discriminating sensors that are wired in parallel. The 1.0 K ohm resistor in the LH supplemental restraint front end discriminating sensor parallel to the normally open switches in both sensors and 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 supplemental 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 checks 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. |
| - | Once 250 malfunction free ignition cycles have occurred. |
Diagnostic Aids
A broken or chafed wire in the supplemental restraint front end discriminating sensor circuit can cause an intermittent condition. Inspect CKT 1834 and CKT 251 carefully for cutting or chafing.
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 an inspection 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 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 251.
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This test inspects for proper contact or corrosion of the supplemental restraint sensing and diagnostic module (SDM) connector.
-
This test inspects for an open in CKT 1834.
-
This test isolates the open in CKT 1834 to one side of C109
-
This test inspects for a short to voltage in CKT 1834.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SRS Diagnostic System Check performed? | -- | ||
Are the terminals damaged or corroded? | -- | |||
3 | Replace the sensor harness connector. Refer to Wiring Repair . Is the repair complete? | -- | -- | |
4 | Inspect for proper connection at the right sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | ||
5 | Inspect for proper connection at the right sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | ||
6 | Replace the right supplemental restraint front end discriminating sensor. Refer to Supplemental Restraint Front End Discriminating Sensor Replacement . Is the repair complete? | -- | -- | |
Measure the resistance between the right sensor connector terminals A and B. Is the resistance reading more than the specified value? | 1050 ohms | |||
Measure the resistance from the right sensor harness connector terminal B to ground. Is the resistance reading within the specified values? | 0-5 ohms | |||
9 |
Are the terminals damaged or corroded? | -- | ||
10 | Replace the left sensor connector. Refer to Wiring Repair . Is the repair complete? | -- | -- | |
11 | Inspect for proper connection at the left sensor connector terminals C and D. Are the terminals damaged or corroded? | -- | ||
12 | Inspect for proper connection at the left sensor connector terminals C and D. Are the terminals damaged or corroded? | -- | ||
13 | Measure the resistance between the right sensor harness connector terminal B and the left sensor harness connector terminal C. the resistance reading within the specified values? | 0-5 ohms | ||
14 | Repair an open condition in CKT 251 between the two sensors. Is the repair complete? | -- | -- | |
15 | Measure the resistance between the left sensor harness connector terminal D to gorund. Is the resistance reading within the specified values? | 0-5 ohms | ||
16 | Replace the left supplemental restraint front end discriminating sensor. Refer to Supplemental Restraint Front End Discriminating Sensor Replacement . Is the repair complete? | -- | -- | |
17 | Repair an open condition in CKT 251 between the left supplemental restraint front end discriminator sensor harness connector to gorund. Is the repair complete? | -- | -- | |
Is the connector damaged or corroded? | -- | |||
19 | Replace the SDM harness connector. Refer to Wiring Repair . Is the repair complete? | -- | -- | |
20 | Inspect for proper connection at terminal 9 of the SDM. Is the terminal damaged or corroded? | -- | ||
21 | Inspect for proper connection at terminal 9 of the SDM. Is the terminal damaged or corroded? | -- | ||
22 | Replace the supplemental restraint sensing and diagnostic module (SDM). Refer to Supplemental Restraint Sensing and Diagnostic Module Replacement . Is the repair complete? | -- | -- | |
Is the resistance reading within the specified values? | 0-5 ohms | |||
24 |
Are the terminals damaged or corroded? | -- | ||
25 | Replace the left sensor harness connector. Refer to Wiring Repair . Is the repair complete? | -- | -- | |
26 | Inspect for proper connection at the left sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | ||
27 | Inspect for proper connection at the left sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | ||
28 | Measure the resistance between the SDM harness connector terminal 9 and the left sensor harness connector terminal B. Is the resistance reading within the specified values? | 0-5 ohms | ||
29 | Measure the resistance between the left sensor harness connector terminal A and the right sensor harness connector terminal A. Is the resistance reading within the specified values? | 0-5 ohms | ||
30 | Repair an open condition in CKT 1834 between the two sensors. Is the repair complete? | -- | -- | |
31 |
Is the terminal damaged or corroded? | -- | ||
32 | Replace C109. Refer to Wiring Repair . Is the repair complete? | -- | -- | |
Measure the resistance between the sensor harness connector terminal A and the C109 terminal A. Is the resistance reading within the specified values? | 0-5 ohms | |||
34 | Repair an open condition in CKT 1834 between C109 and the SDM harness connector. Is the repair complete? | -- | -- | |
35 | Repair an open condition in CKT 1834 between C109 and the sensor harness connector. Is the repair complete? | -- | -- | |
Is the measured voltage less than the specified value? | 1.0 V | |||
37 |
Is the repair complete? | -- | -- | |
38 | Reconnect all the SRS components. Ensure that all the components are properly mounted. Have all the SRS components been reconnected and properly mounted? | -- | -- | |
39 | Clear all the SRS DTCs. Have all the SRS DTCs been cleared? | -- | -- |
