GM Service Manual Online
For 1990-2009 cars only

Circuit Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform a turn-on test to diagnose critical malfunctions within the SDM itself.

Upon passing these tests, the ignition and deployment loop voltages are measured to ensure that these voltages are within the normal ranges. The SDM monitors the voltages at the driver low and the passenger low to detect shorts to ground or voltage in the deployment loops.

The SDM tests the wiring connection to extra devices, such as the side impact sensor, by letting an infinitesimal current flow through the internal circuit to verify the resistance. If the voltage is out of range, the SDM is unable to test the air bag system properly.

In the case of DTC B1103, test the battery and if necessary replace the battery with a new one. Erase the DTC using the scan tool.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1446 Passenger Seat Occupant Classification System (OCS) Circuit Short to Battery

Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

Conditions for Setting the DTC

The OC sensor wiring is shorted to the battery wiring.

Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Step

Action

Value(s)

Yes

No

Warning: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Warning in the Preface section.

Warning: Refer to Sensing and Diagnostic Module Handling Warning in the Preface section.

Schematic Reference: SIR Schematics

Connector End View Reference: Component Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn the ignition switch to OFF.
  2. Wait 60 seconds for the sensing and diagnostic module (SDM) charger to discharge.

Is the SDM charger discharged?

--

Go to Step 3

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3

Visually inspect for damage to the OC sensor wiring.

Is the OC sensor wiring damaged?

--

Go to Step 4

Go to Step 5

4

Replace the air bag wiring.

Did you complete the replacement?

--

Go to Step 9

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5

  1. Disconnect the OC sensor connector.
  2. Disconnect the SDM connector.
  3. measure the resistance between the terminal 64 of the SDM and the terminal 2 of the OC sensor.

Is the resistance approximately equal to the indicated value?

0 Ω

Go to Step 6

Go to Step 4

6

  1. Test the resistance between the terminal 1 of the OC sensor and terminal 28 of C201 connector.
  2. Test the resistance between the terminal 28 and 30 of C201 connector.

Are the resistances approximately equal to the indicated value?

0 Ω

Go to Step 7

Go to Step 8

7

Replace the OC sensor.

Did you complete the replacement?

--

Go to Step 9

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8

Replace the wiring harness which did not show 0 ohm resistance.

Did you complete the replacement?

--

Go to Step 9

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9

  1. Reconnect all SIR system components.
  2. Verify that all components, connectors, and connector position assurances (CPAs) are properly mounted.
  3. Use the scan tool to clear the DTCs.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the text.

Does the DTC reset?

--

Go to Step 2

System OK