For 1990-2009 cars
SIR Components
Sensors, Pretensioners, and Side Air Bags
SIR Caution
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The ignition switch supplies ignition 1 voltage to the inflatable restraint sensing and diagnostic module (SDM) at terminal A1 using the SDM Fuse. The ignition switch also supplies ignition 1 voltage to the instrument cluster. The AIR BAG warning lamp is controlled by the SDM via Class 2 serial data. When the ignition switch is first turned ON, the instrument cluster flashes the AIR BAG warning lamp seven times. Next, the SDM performs tests on the SIR system then commands the instrument cluster to turn OFF the AIR BAG warning lamp after it has flashed seven times. If the ignition 1 voltage is outside of the normal operating voltage range (9-16 V), the SDM will command the instrument cluster to turn ON the AIR BAG warning lamp with no DTCs present.

### Diagnostic Aids

The loss of serial data communication between the SDM and the instrument cluster will cause the AIR BAG warning lamp to come ON solid. Refer to Data Link Communications Circuit Description in Data Link Communications.

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. This step checks to see if the AIR BAG warning lamp flashes seven times when the ignition is turned ON.

2. This step checks to see if the scan tool can communicate with the instrument panel cluster (IPC).

3. This step checks to see if the ignition voltage to the SDM is greater than 9 V.

4. This step checks to see if the ignition voltage to the SDM is greater than 16 V.

5. This step checks the SDM wiring harness connector.

6. This step checks to see if there is an open or a high resistance in the B+ feed circuit to the SDM.

7. This step checks to see if there is an open or a high resistance in the B+ feed circuit to the SDM Fuse.

8. This step determines if there is an open or a high resistance in the SDM ground circuit or if there is a malfunctioning SDM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform A Diagnostic System Check - SIR? | -- | Go to Step 2 | Go to Diagnostic System Check - SIR
2 |

1. Turn OFF the ignition.
2. Note the AIR BAG warning lamp while turning ON the ignition.

Does the AIR BAG warning lamp flash seven times?

--

Go to Step 4

Go to Step 3

3 | Replace the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console. Did you complete the replacement? | -- | Go to Step 16 | --
4 |

1. Install a scan tool.
2. Attempt to communicate with the instrument panel cluster (IPC).

Does the scan tool communicate with the IPC?

--

Go to Step 5

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

5 | Use the scan tool to request the SIR data list display. Does the scan tool indicate that the ignition voltage is greater than the specified value? | 9 V | Go to Step 6 | Go to Step 7
6 | Does the scan tool indicate that the ignition voltage is greater than the specified value? | 16 V | Go to Diagnostic System Check - Engine Electrical in Engine Electrical | Go to Step 15
7 |

1. Turn OFF the ignition.
2. Disconnect the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
3. Inspect the SDM wiring harness connector for the following conditions:

• | Corrosion

• | Damaged terminals

• | Poor connections/terminal tension

Does the SDM wiring harness connector exhibit any sings of corrosion, terminal damage, or poor connections?

--

Go to Step 8

Go to Step 9

8 | Replace the SDM wiring harness connector. Refer to Connector Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | --
9 |

1. Remove the SDM Fuse.
2. Use the J 39200 Digital Multimeter (DMM) to measure the resistance of the B+ feed circuit from the SDM Fuse to the SDM.

Does the resistance measure less than the specified value?

0.5 ohms

Go to Step 11

Go to Step 10

10 | Locate and repair an open or a high resistance in the B+ feed circuit from the SDM Fuse to the SDM. Did you complete the repair? | -- | Go to Step 16 | --
11 |

1. Turn ON the ignition, with the engine OFF.
2. Use the DMM to measure the voltage between the B+ feed circuit to the SDM Fuse and a known good ground.

Does the voltage measure near the specified value?

12 V

Go to Step 13

Go to Step 12

12 | Locate an open or a high resistance in the B+ feed circuit to the SDM Fuse. Did you complete the repair? | -- | Go to Step 16 | --
13 |

1. Turn OFF the ignition.
2. Use the DMM to measure the resistance between the SDM ground circuit and a know good ground.

Does the resistance measure less than the specified value?

0.5 ohms

Go to Step 15

Go to Step 14

14 | Locate and repair an open or a high resistance in the SDM ground circuit. Did you complete the repair? | -- | Go to Step 16 | --
15 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Did you complete the replacement? | -- | Go to Step 16 | --
16 |

1. Reconnect all SIR and instrument cluster components.
2. Verify that all components and connectors are properly mounted.
3. Turn ON the ignition, with the engine OFF.
4. Use the scan tool in order to clear the DTCs.

Did you complete the action?

--

Go to Diagnostic System Check - SIR

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