Circuit Description
When you first turn the ignition switch to the ON position, the inflatable 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 RH inflatable 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 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 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 inflatable 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 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 checks for proper contact or corrosion of the yellow 2-way connector.
-
This test checks for a malfunctioning discriminating sensor.
-
This test checks for an open in CKT 251.
-
This test checks for proper contact or corrosion of the inflatable restraint Sensing and Diagnostic Module (SDM) connector.
-
This test checks for an open in CKT 1834.
-
This test isolates the open in CKT 1834 to one side of C109
-
This test checks for a short to voltage in CKT 1834.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System Check performed? | -- | ||
Are the terminals damaged or corroded? | -- | |||
3 | Replace the sensor harness connector. Refer to Wiring Repair . Are the repairs complete? | -- | -- | |
4 | Check for proper connection at the RH sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | ||
5 | Check for proper connection at the RH sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | ||
6 | Replace the RH inflatable restraint front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement . Are the repairs complete? | -- | -- | |
Is the resistance reading more than the specified value? | 1050 ohms | |||
Measure the resistance from the RH 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 LH sensor connector. Refer to Wiring Repair . Are the repairs complete? | -- | -- | |
11 | Check for proper connection at the LH sensor connector terminals C and D. Are the terminals damaged or corroded? | -- | ||
12 | Check for proper connection at the LH sensor connector terminals C and D. Are the terminals damaged or corroded? | -- | ||
13 | Measure the resistance between the RH sensor harness connector terminal B and the LH 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. Are the repairs complete? | -- | -- | |
15 | Measure the resistance between the LH sensor harness connector terminal D and ground. Is the resistance reading within the specified values? | 0-5 ohms | ||
16 | Replace the LH inflatable restraint front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement . Are the repairs complete? | -- | -- | |
17 | Repair an open condition in CKT 251 between the LH inflatable restraint front end discriminator sensor harness connector and ground. Are the repairs complete? | -- | -- | |
Is the connector damaged or corroded? | -- | |||
19 | Replace the SDM harness connector. Refer to Wiring Repair . Are the repairs complete? | -- | -- | |
20 | Check for proper connection at terminal 9 of the SDM. Is the terminal damaged or corroded? | -- | ||
21 | Check for proper connection at terminal 9 of the SDM. Is the terminal damaged or corroded? | -- | ||
22 | Replace the inflatable restraint Sensing and Diagnostic Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Are the repairs complete? | -- | -- | |
Is the resistance reading within the specified values? | 0-5 ohms | |||
24 |
Are the terminals damaged or corroded? | -- | ||
25 | Replace the LH sensor harness connector. Refer to Wiring Repair . Are the repairs complete? | -- | -- | |
26 | Check for proper connection at the LH sensor connector terminals A and B. Are the terminals damaged or corroded? | -- | ||
27 | Check for proper connection at the LH 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 LH sensor harness connector terminal B. Is the resistance reading within the specified values? | 0-5 ohms | ||
29 | Measure the resistance between the LH sensor harness connector terminal A and the RH 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. Are the repairs complete? | -- | -- | |
31 |
Is the terminal damaged or corroded? | -- | ||
32 | Replace C109. Refer to Wiring Repair . Are the repairs complete? | -- | -- | |
Measure the resistance between the LH sensor harness connector terminal B 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. Are the repairs complete? | -- | -- | |
35 | Repair an open condition in CKT 1834 between C109 and the sensor harness connector. Are the repairs complete? | -- | -- | |
Is the measured voltage less than the specified value? | 1.0 V | |||
37 |
Are the repairs complete? | -- | -- | |
38 | Reconnect all the SIR system components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | -- | |
39 | Clear all the SIR DTCs. Have all the SIR DTCs been cleared? | -- | -- |
