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 procedure will help you to find and repair SIR system malfunctions. For best results, use the diagnostic tables and follow the sequence listed below:

1. Perform the SIR Diagnostic System Check. The SIR Diagnostic System Check must be the starting point of any SIR diagnostics. The SIR Diagnostic System Check tests for the following conditions:

• | Proper AIR BAG warning lamp operation

• | The ability of the SDM to communicate through the Data Link Connector (DLC)

• | The existence of SIR Diagnostic Trouble Codes (DTCs)

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:

• | 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 uses the AIR BAG Fuse for supplying Ignition 1 voltage to the inflatable restraint Sensing and Diagnostic Module (SDM) at terminal 8. When you first turn the ignition switch to the ON position, the SDM responds by flashing the AIR BAG warning lamp seven times. Then the SDM turns the lamp Off, while performing tests on the SIR system.

### Diagnostic Aids

Diagnosing DTCs in the correct order is very important. Failure to diagnose DTCs in the order specified may result in the following:

• | Extended diagnostic time

• | Incorrect diagnosis

• | Incorrect parts replacement

### Test Description

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

1. This step confirms that the AIR BAG warning lamp should flash seven times after you first turn the ignition to the ON position.

2. The AIR BAG warning lamp indicates improper operation. This step differentiates between a warning lamp which stays in the ON position and a warning lamp that does not come ON.

3. This step confirms that the AIR BAG warning lamp should turn OFF after flashing seven times.

4. This step determines whether the SDM is flashing DTC 12.

5. This step checks for proper operation of the serial data line.

6. This step identifies the stored diagnostic trouble codes and tells whether they are current or history.

7. This step checks for the proper operation of the serial data line. This step also identifies any stored history diagnostic trouble codes.

#### SIR Diagnostic System Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Observe the AIR BAG warning lamp while you turn the ignition switch to the ON position. Does the AIR BAG warning lamp flash seven times? | -- | Go to Step 3 | Go to Step 2
2 | Does the AIR BAG warning lamp come ON steady? | -- | Go to AIR BAG Warning Lamp Comes On Steady | Go to AIR BAG Warning Lamp Does Not Come On
3 | Note the AIR BAG warning lamp after the lamp has flashed seven times. Does the AIR BAG warning lamp turn OFF? | -- | Go to Step 8 | Go to Step 4
4 | Does the warning lamp flash seven times and then come on steady? | -- | Go to Step 5 | Go to Lamp Flashes Seven Times, Then DTC 12
5 |

1. Turn the ignition switch to the LOCK position.
2. Connect a scan tool to the data link connector. Follow the directions in the instruction manual of the scan tool.
3. Turn the ignition switch to the ON position.
4. Request the SIR diagnostic trouble code display.

Does a current DTC display?

--

Go to Step 7

Go to Step 6

6 | Does the scan tool indicate that no data has been received? | -- | Go to Scan Tool Does Not Communicate with UART Data Line in Wiring Systems | Go to Integrity Check
7 |

1. Turn the ignition switch to the LOCK position.
2. Record the displayed DTC(s) on the repair order, specifying as either current or history.

• | When DTC B1051 is set, go to DTC B1051 Deployment Commanded .

• | When DTC B1019 is set, go to DTC B1019 Passenger Deploy. Loop Short to Voltage .

• | When DTC B1025 is set, go to DTC B1025 Driver Deployment Loop Short to Voltage .

3. Diagnose the remaining current DTC(s) from the lowest to the highest.
4. When only history DTCs exist, refer to the Diagnostic Aids section for each specific DTC. A history DTC indicates that the malfunction has been repaired or is intermittent.

Have you performed the current DTC diagnosis and have you cleared all the current DTCs?

--

Go to Step 1

--

8 |

1. Turn the ignition switch to the LOCK position.
2. Connect a scan tool to the data link connector. Follow the directions in the instruction manual for the scan tool.
3. Turn the ignition switch to the ON position.
4. Request the SIR diagnostic trouble code display.

Is a history DTC displayed?

--

Go to Step 10

Go to Step 9

9 | Does the scan tool indicate that no data has been received? | -- | Go to Scan Tool Does Not Communicate with UART Data Line in Wiring Systems | System OK
10 |

1. Turn the Ignition switch to the LOCK position.
2. Record the displayed DTC(s) on the repair order specifying as history.
3. When DTC B1071 is set, go to DTC B1071 Internal SDM Failure .
4. For all other DTCs, refer to the Diagnostic Aids section for that specific DTC. A history DTC indicates that the malfunction was repaired or the malfunction is intermittent, but that no one has yet cleared the DTC.

Have you performed the diagnosis and have you cleared the DTC?

--

Go to Step 1

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