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. Next the SDM measures the following circuits to ensure they are within their respective normal voltage ranges:
| • | Ignition Positive Voltage |
| • | 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 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 Positive Voltage 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 2160 and CKT 1851 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 1851.
-
This test isolates the open in CKT 1851 to one side of C101.
-
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 2160.
-
This test isolates the open in CKT 2160 to one side of C101.
-
This test checks for a short to voltage in CKT 2160.
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 C101. Refer to SIR Components Is the repair complete? | -- | Go to Step 27 | -- |
Measure the resistance between the sensor harness connector terminal B and C101. 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 1851 between C101 and G304. Is the repair complete? | -- | Go to Step 27 | -- |
13 | Repair an open condition in CKT 1851 between C101 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 SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Is the repair complete? | -- | Go to Step 27 | -- |
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 C101. 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 C101 terminal A. Is the resistance reading within the specified value? | 0-5 ohms | Go to Step 23 | Go to Step 24 | |
23 | Repair an open condition in CKT 2160 between C101 and the SDM harness connector. Is the repair complete? | -- | Go to Step 27 | -- |
24 | Repair an open condition in CKT 2160 between C101 and the sensor harness connector. Is the repair complete? | -- | Go to Step 27 | -- |
Is the measured voltage less than the specified value? | 1.0 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? | -- | -- |
