For 1990-2009 cars
SIR Components
SIR Schematics
SIR Caution
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

When the ignition switch is first turned to OFF/UNLOCK or RUN, IGNITION 1 voltage is applied from the CLS/PCM fuse to the INDICATORS bus in the IPC. The ground side of the AIR BAG indicator (LED) is controlled by the instrument cluster microprocessor. When the ignition switch is in the OFF/UNLOCK position, the serial data line (CKT 800) is not operative. This condition will cause the IPC microprocessor to turn the AIR BAG (as well as the SEAT BELT) indicator ON steady. When the ignition switch is first turned to RUN, the AIR BAG Fuse applies battery voltage to the IGNITION 1 input, terminal 10. The inflatable restraint sensing and diagnostic module (SDM) responds by flashing the AIR BAG indicator (via the serial data line) seven times. If IGNITION 1 is outside of the normal operating voltage range (8.2-17.1 volts), the AIR BAG indicator will come ON steady with no DTCs set.

### Diagnostic Aids

If the serial data line is malfunctioning, the AIR BAG indicator will come on steady. If the inflatable restraint sensing and diagnostic module (SDM) connector is not properly connected to the SDM, the AIR BAG indicator will come ON steady.

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:

1. This test checks for a malfunction in the serial data line (CKT 800).

2. This test checks for sufficient IGNITION 1 voltage applied to the SDM.

3. This test checks for excessive IGNITION 1 voltage applied to the SDM.

4. This test checks for a proper connection at the SDM.

5. An open AIR BAG Fuse would cause the AIR BAG warning lamp to come on steady.

6. This test checks whether a short to ground caused the AIR BAG Fuse to open.

7. This test determines whether the short to ground is due to a short in the wiring or internal to the SDM.

8. This test checks for an open in the IGNITION 1 circuit, CKT 1139.

#### AIR BAG Warning Lamp Comes On Steady

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the SIR Diagnostic System Check performed? | -- | Go to Step 2 | Go to SIR Diagnostic System Check
2 |

1. Turn the ignition switch to the OFF position.
2. Connect a scan tool to the Data Link Connector (DLC).
3. Turn the ignition switch to the RUN position.
4. Request the SIR data list display.

Does scan tool indicate no data received?

--

Go to Step 3

Go to Step 4

3 | Request diagnostic data from other modules (IPC, PCM, etc.) Does scan tool indicate no data received? | -- | Go to Scan Tool Does Not Communicate with Components in Wiring Systems | Go to Step 5
4 | Using the scan tool, request the SIR data list display. Is IGNITION more than the specified value? | 8.2 V | Go to Step 5 | Go to Step 8
5 |

1. Set the parking brake.
2. Start the engine.
3. Using the scan tool, read the SIR data list.

Is IGNITION more than the specified value?

17.1 V

Go to Charging System Check

Go to Step 6

6 |

1. Turn the ignition switch to the OFF position.
2. Inspect the inflatable restraint Sensing and Diagnostic Module (SDM) harness connector CPA.

Is the CPA properly installed?

--

Go to Step 8

Go to Step 7

7 | Connect the SDM harness connector securely to the SDM. Are the repairs complete? | -- | Go to SIR Diagnostic System Check | --
8 |

1. Turn the ignition switch OFF.
2. Remove the AIR BAG Fuse.
3. Inspect the AIR BAG Fuse.

Is the AIR BAG Fuse good?

--

Go to Step 14

Go to Step 9

9 |

1. Replace the AIR BAG Fuse.
2. Turn the ignition switch to the RUN position for 10 seconds.
3. Turn the ignition switch OFF.
4. Remove the AIR BAG Fuse.
5. Inspect the AIR BAG Fuse.

Is the AIR BAG Fuse good?

--

Go to Step 13

Go to Step 10

10 |

1. Disconnect the SDM.
2. Replace the AIR BAG Fuse.
3. Turn the ignition switch to the RUN position for 10 seconds.
4. Turn the ignition switch to the OFF position.
5. Remove the AIR BAG Fuse.
6. Inspect the AIR BAG Fuse.

Is the AIR BAG Fuse good?

--

Go to Step 12

Go to Step 11

11 |

1. Repair a short to ground condition in CKT 1139.
2. Reconnect the SDM.
3. Replace the AIR BAG Fuse.

Are the repairs complete?

--

Go to Step 16

--

12 |

1. Replace the inflatable restraint Sensing and Diagnostic Module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
2. Install the AIR BAG Fuse.

Are the repairs complete?

--

Go to Step 16

--

13 | Install the AIR BAG Fuse. Are the repairs complete? | -- | Go to Step 16 | --
14 | Measure the resistance from the SDM harness connector terminal 10 to each terminal of the AIR BAG Fuse fuseholder. Is either resistance reading within the specified values? | 0-5 ohms | Go to Integrity Check | Go to Step 15
15 | Repair an open condition in CKT 1139. Are the repairs complete? | -- | Go to Step 16 | --
16 | Reconnect all the SIR system components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | Go to SIR Diagnostic System Check | --