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

### Circuit Description

The inflatable restraint sensing and diagnostic and seat belt pretensioner module (SDM) performs tests to diagnose critical malfunctions within itself when the ignition switch is turned ON. The SDM is hard-wired to the body control module (BCM) through CKT XY999. When the ignition switch is turned to the ON position, the SDM sends fixed frequency pulses to the BCM. In the event of a collision involving air bag deployment, the SDM sends higher frequency pulses to the BCM, which in turn sends a Class 2 message to the ONSTAR module. Upon receiving the Class 2 message, the ONSTAR module transmits a deployment commanded output (DCO) signal to the service center via the vehicle's cellular telephone. The SDM monitors CKT XY999 to detect leakage currents to voltage and open circuits in the (DCO) link to the BCM. The SDM service wait time is 1 minute. Refer to ENABLE/DISABLE procedures.

### Conditions for Setting the DTC

DTC 98 will set when there is a short to ground in CKT XY999.

### Action Taken When the DTC Sets

• | The SDM sets a DTC 98.

• | The SDM turns ON the AIR BAG warning lamp.

### Conditions for Clearing the DTC

Current and History DTC codes must be cleared using a scan tool Clear DTC Information command. If the circuit fault has been successfully repaired and the conditions which caused the DTC to set are no longer existing, the DTC may be cleared using the scan tool.

### Diagnostic Aids

A short to ground in CKT XY999 can cause an intermittent condition. Inspect CKT XY999 carefully for cutting and/or chafing. A careful inspection of the circuit and components indicated on the DTC 98 table is essential to make sure that the SDM and/or BCM will not be unnecessarily replaced.

### Test Description

1. This step checks the inflatable restraint sensing and diagnostic and seat belt pretensioner module (SDM) wiring harness connector for damaged terminals or corrosion.

2. This step checks the inflatable restraint sensing and diagnostic and seat belt pretensioner module (SDM) for damaged terminals or corrosion.

3. This step checks the body control module (BCM) wiring harness connector C1 for damaged terminals or corrosion.

4. This step checks the body control module (BCM) for damaged terminals or corrosion.

5. This step checks for a short to ground in CKT XY999.

6. This step determines if there is a malfunctioning BCM or if there is a malfunctioning SDM.

#### DTC 98 ONSTAR DCO Link Short to Ground

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. Disconnect the inflatable restraint sensing and diagnostic and seat belt pretensioner module (SDM) wiring harness connector. Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement .
2. Inspect terminal 40 of the SDM wiring harness connector for damaged terminals or corrosion.

Is the terminal 40 of the SDM wiring harness connector damaged or corroded?

--

Go to Step 3

Go to Step 4

3 | Use the J 42250 Catera Terminal Repair Kit to repair the SDM wiring harness connector. Is the repair complete? | -- | Go to Step 4 | --
4 | Inspect terminal 40 of the SDM for damaged terminals or corrosion. Is the terminal 40 of the SDM damaged or corroded? | -- | Go to Step 5 | Go to Step 6
5 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module Replacement . Is the repair complete? | -- | Go to Step 14 | --
6 |

1. Disconnect the body control module (BCM) wiring harness connector. Refer to Body Control Module Replacement in Body Control System.
2. Inspect terminal A05 of the BCM wiring harness connector C1 for damaged terminals or corrosion.

Is terminal A05 of the BCM wiring harness connector C1 damaged or corroded?

--

Go to Step 7

Go to Step 8

7 | Repair the BCM wiring harness connector C1. Refer to Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 8 | --
8 | Inspect terminal A05 of the BCM for damaged terminals or corrosion. Is terminal A05 of the BCM damaged or corroded? | -- | Go to Step 9 | Go to Step 10
9 | Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Is the repair complete? | -- | Go to Step 14 | --
10 | Use the J 39200 Digital Multimeter (DMM) to measure the resistance between terminal 40 of the SDM wiring harness connector and a known good ground. Is the measured resistance less than the specified value? | OL | Go to Step 11 | Go to Step 12
11 |

1. Locate a short to ground in CKT XY999.
2. Repair the short to ground in CKT XY999.

Is the repair complete?

--

Go to Step 14

--

12 |

1. Connect the SDM wiring harness connector.
2. Connect the BCM wiring harness connector C1.
3. Turn the ignition switch to the ON position.
4. Install the scan tool.
5. Use the scan tool to request the BCM Inputs.
6. Read the communication status of the ONSTAR test flag.
7. Under proper operating conditions, the ONSTAR test flag will display SET.
8. Read the units displayed for the ONSTAR signal.
9. Under proper operating conditions, the ONSTAR signal will display OK.

Does the ONSTAR test flag display SET and the ONSTAR signal display OK?

--

Go to Sensing and Diagnostic Module Integrity Check

Go to Step 13

13 | Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Is the repair complete? | -- | Go to Step 14 | --
14 | Reconnect all the SIR components, making sure all the components are properly mounted? Have all the SIR components been reconnected and properly mounted? | -- | Go to Step 15 | --
15 | Use the scan tool to clear all SIR and BCM current and history DTCs. Have all SIR and BCM current and history DTCs been cleared? | -- | Go to SIR Diagnostic System Check | --