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.

The test ignition and deployment loop voltages are measured to ensure that they are within their normal voltage ranges. The SDM monitors the voltages at the driver low and the passenger low to detect shorts to ground or voltage in the deploy loops.

The SDM inspects the wiring connection to the passenger air bag module by letting the infinitesimal current flow through the internal circuit and verify the resistance. If the voltage is out of range, the SDM is unable to inspect the air bag system properly.

Conditions for Setting the DTC

The voltage supplied from the battery is lower than 10.6 volts.

Step

Action

Values

Yes

No

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

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

 

1

Perform the Diagnostic System Check - SIR.

Is the Diagnostic System Check - SIR complete?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

Inspect the fuse F8.

Is the fuse open?

--

Go to Step 3

Go to Step 4

3

  1. Inspect for a short circuit.
  2. Repair if needed.
  3. Replace the fuse.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

4

  1. Turn the ignition ON.
  2. Using a multimeter, measure the voltage at the fuse F8.

Is the battery voltage available at the fuse F8?

11-14 V

Go to Step 6

Go to Step 5

5

Repair the power supply to the fuse F8.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

6

  1. Disconnect the negative battery cable.
  2. Wait 1 minute before proceeding.
  3. Disconnect the connector at the sensing and diagnostic module (SDM).
  4. Reconnect the battery.
  5. Turn the ignition key ON.
  6. Measure the voltage at the terminal 5 of the SDM connector.

Is the voltage equal to the specified value?

11-14 V

Go to Step 7

Go to Step 8

7

  1. Replace the SDM.
  2. Reconnect the electrical connectors.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

8

  1. Disconnect the connector C214.
  2. The connector C214 is the connector between the instrument harness and the supplemental inflatable restraint (SIR) harness.

  3. Turn the ignition ON.
  4. Using a multimeter, measure the voltage on the instrument harness side at terminal 3 of the connector C214.

Is the voltage equal to the specified value?

11-14 V

Go to Step 9

Go to Step 10

9

  1. Replace the SIR wiring harness.
  2. Reconnect the battery.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

10

Repair the open circuit between the fuse F8 and the connector C214.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--