For 1990-2009 cars

Caution: In order to avoid deploying the air bag when troubleshooting the SIR system, use only the equipment specified in this manual and the instructions given in this manual. Failure to use the specified equipment as instructed could cause air bag deployment, personal injury to you or someone else, or unnecessary SIR system repairs.

Caution: If any water enters the vehicle's interior up to the level of the carpet or higher and soaks the carpet, the sensing and diagnostic module (SDM) and the SDM harness connector may need to be replaced. The SDM could be activated when powered, which could cause deployment of the air bag(s) and result in personal injury. Before attempting these procedures, the SIR system must be disabled. Refer to Disabling the SIR System.

With the ignition OFF, inspect the SDM mounting area, including the carpet. If any significant soaking or evidence of significant soaking is detected, you must perform the following tasks:

1. Remove all water.
2. Repair the water damage.
3. Replace the SDM harness connector.
4. Replace the SDM.

Failure to follow these tasks could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs.

These diagnostic procedures will help you to find and repair SIR system malfunctions. This service category also contains information for repairing SIR system malfunctions. For best results, use the diagnostic tables, and follow the sequence listed below:

1. Perform the SIR Diagnostic System Check. All SIR diagnostics must begin with the SIR Diagnostic System Check. The SIR Diagnostic System Check determines the following items:

• | Proper AIR BAG warning lamp operation

• | Ability of the SDM to communicate through the data link connector (DLC)

• | Existence of SIR Diagnostic Trouble Codes (DTC)

2. Refer to the diagnostic table as directed by the SIR Diagnostic System Check. The diagnostic tables will help enable you to diagnose any SIR system malfunction. Bypassing these procedures may result in the following conditions:

• | Extended Diagnostic Time

• | Incorrect Diagnosis

• | Incorrect Parts Replacement

3. Repeat the SIR Diagnostic System Check after you perform any repair or diagnostic procedures. This will verify that you correctly performed the repair. This will also ensure that no other malfunctions exist.

### Circuit Description

The ignition switch supplies Ignition Positive Voltage to the inflatable restraint sensing and diagnostic module (SDM) at terminal 10 using the AIR BAG Fuse. When the ignition switch is first turned to the RUN position, the SDM responds by flashing the AIR BAG warning lamp 7 times, then turning the lamp OFF, while performing tests on the SIR system.

### Diagnostic Aids

You must diagnose the diagnostic trouble codes in the order specified by the SIR Diagnostic System Check. Failure to do so may result in the following conditions:

• | Extended Diagnostic Time

• | Incorrect Diagnosis

• | Incorrect Parts Replacement

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Attempt to establish communication with the inflatable restraint sensing and diagnostic module (SDM) using a scan tool.

2. Attempt to establish communication with the powertrain control module (PCM). This checks to see if other modules not communicating.

3. This test checks for any SDM DTCs.

4. The AIR BAG warning lamp should flash seven times after the ignition switch is first turned to the RUN position.

5. The AIR BAG warning lamp indicates improper operation. This test differentiates a warning lamp stays ON condition from a warning lamp does not come ON condition.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Reconnect all previously disconnected components.
2. Install a scan tool into the data link connector (DLC).
3. Turn the ignition switch to the RUN position, engine off.
4. Establish communication with the inflatable restraint sensing and diagnostic module (SDM).

Does the scan tool communicate with the SDM?

--

Go to Step 3

Go to Step 2

2 | Does the scan tool communicate with other modules on the UART serial data line? | -- | Go to Sensing and Diagnostic Module Integrity Check | Go to Data Link Communications System Check in Data Link Communications
3 | Use the scan tool in order to read the SIR DTCs. Are there any current and/or history Diagnostic Trouble Codes (DTCs)? | -- | Go to Diagnostic Trouble Code (DTC) List/Type | Go to Step 4
4 |

1. Disconnect the scan tool.
2. Turn the ignition switch to the RUN position, engine off.
3. Note the AIR BAG warning lamp while turning the ignition switch to the RUN position.

Does the AIR BAG warning lamp flash seven times?

--

System OK

Go to Step 5

5 | Does the AIR BAG warning lamp come ON and stay ON? | -- | Go to AIR BAG Warning Lamp Comes On Steady | Go to AIR BAG Warning Lamp Does Not Come On