Circuit Description
The inflatable restraint sensing and diagnostic module (SDM) monitors the front end discriminating sensor circuit for front impact detection. The SDM processes the signal provided by the front end discriminating sensor to further support deployment of the air bags. The front end discriminating sensor is an input only to the SDM and does not directly cause air bag deployment. 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 itself. The SDM then performs the following continuous diagnostic tests on the deployment loops:
| • | Deployment loop voltage out of range test |
| • | Deployment loop resistance measurement test |
If the voltage out of range test detects a short to voltage condition, the resistance measurement test for that deployment loop will not be performed.
Conditions for Setting the DTC
The SDM detects the voltage at the discriminating sensor signal input is greater than 3.65 volts for 300 milliseconds.
Action Taken When the DTC Sets
The SDM commands ON the AIR BAG warning lamp via Class 2 serial data.
Conditions for Clearing the DTC
| • | The voltage at the disriminating sensor signal input is 3.65 volts or less for 300 milliseconds. |
| • | You issue a scan tool CLEAR CODES command. |
| • | A history DTC will clear once 255 malfunction free ignition cycles have occurred. |
When the SDM detects that no DTCs are present, the SDM commands the AIR BAG warning lamp OFF.
Diagnostic Aids
A broken or chafed wire in the inflatable restraint front end discriminating sensor circuit may cause an intermittent condition to occur. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
Tests for proper terminal contact of the yellow 2-way connector.
-
Tests for a malfunctioning discriminating sensor.
-
Tests for an open in the discriminating sensor ground circuit.
-
Test isolates an open in the discriminating sensor ground circuit to one side of the in-line connector.
-
Tests for proper terminal contact of the inflatable restraint sensing and diagnostic module (SDM) connector.
-
Tests for an open in the discriminating sensor signal circuit.
-
Test isolates an open in the discriminating sensor signal circuit to one side of the in-line connector.
-
Tests for a short to voltage in the discriminating sensor signal circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the SIR Diagnostic System Check? | -- | Go to Step 2 | |
Do the terminals exhibit any signs of damage or corrosion? | -- | Go to Step 3 | Go to Step 4 | |
3 | Repair or replace the discriminating sensor harness connector. Refer to Connector Repairs in wiring systems. Did you complete the replacement? | -- | Go to Step 25 | -- |
4 | Check for proper connection at the discriminating sensor connector terminals. Do the terminals exhibit any signs of damage or corrosion? | -- | Go to Step 24 | Go to Step 5 |
Does the resistance measure more than the specified value? | 1050 ohms | Go to Step 24 | Go to Step 6 | |
Using J 39200 DMM measure the resistance from the discriminating sensor harness connector terminal B to ground. Refer to Circuit Testing in Wiring Systems. Does the resistance measure within the specified value? | 0-5 ohms | Go to Step 12 | Go to Step 7 | |
7 |
Do the terminals exhibit any signs of damage or corrosion? | -- | Go to Step 8 | Go to Step 9 |
8 | Repair or replace the discriminating sensor in-line harness connector. Refer to Connector Repairs in Wiring Systems. Did you complete the replacement? | -- | Go to Step 25 | -- |
Using J 39200 DMM measure the resistance between the discriminating sensor harness connector terminal B and the discriminating sensor in-line harness connector terminal B. Refer to Circuit Testing in Wiring Systems. Does the resistance measure within the specified value? | 0-5 ohms | Go to Step 10 | Go to Step 11 | |
10 | Locate and repair an open in the discriminating sensor ground circuit between the in-line harness connector and the inflatable restraint sensing and diagnostic module (SDM). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 25 | -- |
11 | Locate and repair an open in the discriminating sensor ground circuit bewteen the discriminating sensor connector and the discriminating sensor in-line harness connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 25 | -- |
Does the connector exhibit any signs of damage or corrosion? | -- | Go to Step 13 | Go to Step 14 | |
13 | Repair or replace the inflatable restraint sensing and diagnostic module (SDM) harness connector. Refer to Connector Repairs in Wiring Systems. Did you complete the replacement? | -- | Go to Step 25 | -- |
14 | Check for proper connection at the inflatable restraint sensing and diagnostic module (SDM) connector terminals. Do the terminals exhibit any signs of damage or corrosion? | -- | Go to Step 23 | Go to Step 15 |
Does the resistance measure within the specified value? | 0-5 ohms | Go to Step 21 | Go to Step 16 | |
16 |
Do the terminals exhibit any signs of damage or corrosion? | -- | Go to Step 17 | Go to Step 18 |
17 | Repair or replace the discriminating sensor in-line harness connector. Refer to Connector Repairs in Wiring Systems. Did you complete the replacement? | -- | Go to Step 25 | -- |
Using J 39200 DMM measure the resistance of the discriminating sensor input circuit between the discriminating sensor harness connector and the discriminating sensor in-line harness connector. Refer to Circuit Testing in Wiring Systems. Does the resistance measure within the specified value? | 0-5 ohms | Go to Step 19 | Go to Step 20 | |
19 | Locate and repair an open in the discriminating sensor input circuit between the discriminating sensor in-line harness connector and the inflatable restraint sensing and diagnostic module (SDM) harness connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 25 | -- |
20 | Locate and repair an open in the discriminating sensor input circuit between the discriminating sensor in-line harness connector and the discriminating sensor harness connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 25 | -- |
Does the voltage measure less than the specified value? | 1.0 V | Go to Step 22 | ||
22 |
Did you complete the repair? | -- | Go to Step 25 | -- |
23 | Replace the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- |
24 | Replace the inflatable restraint front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- |
25 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
