Circuit Description
The passenger frontal air bag deployment loop is a 2 wire circuit. One wire is the high side of the loop while the other is the low side of the loop. When you first turn the ignition switch ON, the supplemental restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. Then the SDM 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 Running the DTC
The SDM monitors the passenger frontal air bag deployment loop at power on and continuously there after.
Conditions for Setting the DTC
| • | If the SDM detects the resistance between the high side and the low side of the deployment loop is greater than 4.8 ohms for 5 consecutive samples, the SDM sets this DTC. |
| • | Passenger frontal high is less than 2.4 volts and passenger frontal loop resistance is greater than or equal to 6 ohms for 5 consecutive samples, the SDM sets this DTC. |
The passenger frontal deployment loop consists of the following components:
| • | Supplemental restraint IP module. |
| • | Harness wiring of passenger frontal high and low deployment circuits. |
| • | Connector terminal contact. |
Action Taken When the DTC Sets
| • | The SDM sets a DTC. |
| • | The SDM commands ON the AIR BAG warning lamp via Class 2 serial data. |
The SDM also sets this DTC as current after an accident. The SDM will write the status of this DTC to the "crash log" area of the EEPROM for retrieval.
Conditions for Clearing the DTC
| • | Current DTC |
| - | Passenger frontal deployment loop resistance is less than or equal to 4.8 ohms for 5 consecutive samples. |
| - | Passenger frontal high is greater than 2.4 volts, passenger frontal loop resistance is less than 6 ohms for 5 consecutive samples. |
| - | CLEAR CODES command |
| • | History DTC |
| - | You issue a scan tool CLEAR CODES command. |
| - | 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 to be turn OFF. |
Diagnostic Aids
If the DTC is stored as a history DTC the deployment circuit must be checked for:
| • | Frayed insulation |
| • | Damaged connectors |
| • | Moisture damage |
| • | Stretched/broken wires |
The fact that the DTC set and is now stored as a history DTC indicates a short between the two sides of the deployment circuit has happened in the past. The short will prevent deployment if it happens again during a commanded air bag deployment.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
-
This step checks the IP/passenger inflator module in-line connector.
-
This step checks to see if there is a malfunctioning supplemental restraint passenger frontal module.
-
This step checks to see if the supplemental restraint sensing and diagnostic module (SDM) wiring harness connector is OK.
-
This step checks to see if there is an open or high resistance in the passenger frontal high deployment circuit.
-
This step determines if there is an open or high resistance in the passenger frontal low deployment circuit or if there is a malfunctioning SDM.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the A Diagnostic System Check-SRS? | -- | ||||||||
Does connector exhibits any signs of corrosion, terminal damaged, or poor connections? | -- | |||||||||
3 | Replace the wiring harness side of in-line connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you complete the replacement? | -- | -- | |||||||
4 |
Is DTC retrieved as current? | -- | Go to Diagnostic Aids | |||||||
Is DTC retrieved as current? | -- | |||||||||
6 |
Did you complete the replacement? | -- | -- | |||||||
Is the supplemental restraint sensing and diagnostic module (SDM) connector OK? | -- | |||||||||
8 | Repair or replace the supplemental restraint sensing and diagnostic module (SDM) wiring harness connector. Refer to Connector Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
Using the DMM measure the resistance of passenger frontal high circuit between in-line connector terminal and the supplemental restraint sensing and diagnostic module (SDM) wiring harness connector. Is the measured resistance within the specified value? | 0-0.5 ohms | |||||||||
10 | Locate and repair the open or a high resistance in passenger frontal high deployment circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
Using the J 39200 measure the resistance of passenger frontal low circuit between in-line connector terminal and the supplemental restraint sensing and diagnostic module (SDM) wiring harness connector. Is the measured resistance within the specified value? | 0-0.5 ohms | |||||||||
12 | Locate and repair the open or a high resistance in passenger frontal low deployment circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
13 | Replace the supplemental restraint sensing and diagnostic module (SDM). Refer to Supplemental Restraint Sensing and Diagnostic Module Replacement . Did you complete the replacement? | -- | -- | |||||||
14 |
Did you complete the action? | -- | System OK |
