GM Service Manual Online
For 1990-2009 cars only

Object Number: 541416  Size: SF
SIR Components
SIR Schematics
SIR Schematic Icons
SIR Schematic Icons
SIR Schematic Icons

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 inflatable 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:

    • Inflatable 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 a Passenger Air Bag deployment. 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.

  1. This step checks the IP/passenger inflator module in-line connector.

  2. This step checks to see if there is a malfunctioning inflatable restraint passenger frontal module.

  3. This step checks to see if the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector is OK.

  4. This step checks to see if there is an open or high resistance in the passenger frontal high deployment circuit.

  5. 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-SIR?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

  1. Turn OFF the ignition.
  2. Disconnect inflatable restraint IP/passenger inflator module in-line connector.
  3. Inspect the wiring harness in-line connector for the following conditions:
  4. • Corrosion
    • Terminal damaged
    • Poor connections/terminal tension

Does connector exhibits any signs of corrosion, terminal damaged, or poor connections?

--

Go to Step 3

Go to Step 4

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?

--

Go to Step 14

--

4

  1. Reconnect inflatable restraint IP module in-line connector.
  2. Make sure that the connector position assurance (CPA) is properly installed.
  3. Install a scan tool.
  4. Turn ON the ignition, with the engine OFF.
  5. Use the scan tool to retrieve DTCs.

Is DTC retrieved as current?

--

Go to Step 5

Go to Diagnostic Aids

5

  1. Turn OFF the ignition.
  2. Disconnect in-line connector.
  3. Install the J 38715-A SIR Load Tool to the wiring harness side of in-line connector. Use appropriate connector adaptors where necessary.
  4. Turn ON the ignition, with the engine OFF.
  5. Use the scan tool to retrieve DTCs.

Is DTC retrieved as current?

--

Go to Step 7

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Replace the inflatable restraint passenger inflator module. Refer to Inflatable Restraint Instrument Panel Module Replacement .

Did you complete the replacement?

--

Go to Step 14

--

7

  1. Turn OFF the ignition.
  2. Remove the J 38715-A SIR Load Tool.
  3. Disconnect the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  4. Check for proper connection of passenger frontal high and low deployment circuit terminals of the inflatable restraint sensing and diagnostic module (SDM) connector.

Is the inflatable restraint sensing and diagnostic module (SDM) connector OK?

--

Go to Step 9

Go to Step 8

8

Repair or replace the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

9

Using J 39200 DMM measure the resistance of passenger frontal high circuit between in-line connector terminal and the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector.

Is the measured resistance within the specified value?

0-0.5 ohms

Go to Step 11

Go to Step 10

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?

--

Go to Step 14

--

11

Using the J 39200 measure the resistance of passenger frontal low circuit between in-line connector terminal and the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector.

Is the measured resistance within the specified value?

0-0.5 ohms

Go to Step 13

Go to Step 12

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?

--

Go to Step 14

--

13

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 14

--

14

  1. Reconnect all SIR components.
  2. Verify that all components, connectors and CPAs are properly mounted.
  3. Clear the DTCs using the scan tool.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Did you complete the action?

--

System OK Diagnostic System Check - SIR

Go to Diagnostic Aids