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 voltage continuously from the warning lamp terminal.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2501 Passenger Air Bag Disabled Indicator Circuit Malfunction

Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

Conditions for Setting the DTC

The passenger ON indicator lamp does not operate depending on the status of passenger presence.

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

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.

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Did you perform a Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Inspect the fuse F3.

Is fuse F3 blown?

--

Go to Step 3

Go to Step 4

3

Replace the fuse F3.

Did you complete the replacement?

--

Go to Step 15

--

4

  1. Confirm that the ignition switch is ON.
  2. Remove the clock assembly.
  3. Measure the voltage from the fuse F3.

Is the voltage within the indicated range?

9-14 V

Go to Step 6

Go to Step 5

5

Repair the power supply and the wiring to the fuse F3.

Did you complete the repair?

--

Go to Step 15

--

6

  1. Confirm that the ignition switch is OFF.
  2. Remove the clock.
  3. Inspect the bulb of the passenger air bag ON indicator.

Is the bulb OK?

--

Go to Step 8

Go to Step 7

7

Replace the bulb.

Did you complete the replacement?

--

Go to Step 15

--

8

  1. Confirm that the ignition switch is ON.
  2. Measure the voltage from terminal 1 of the clock wiring connector.

Is the voltage within the indicated range?

9-14 V

Go to Step 10

Go to Step 9

9

Repair the wiring between the fuse F3 and the terminal 1 of the clock wiring connector.

Did you complete the repair?

--

Go to Step 15

--

10

Inspect the connection between terminal 1 and terminal 9 of the clock.

Is the connection OK?

--

Go to Step 12

Go to Step 11

11

Replace the clock assembly.

Did you complete the replacement?

--

Go to Step 15

--

12

  1. Confirm that the ignition switch is OFF.
  2. Disconnect the sensing and diagnostic module (SDM) connector.
  3. Confirm that the ignition switch is ON.
  4. Measure the resistance between terminal 67 of the SDM and terminal 9 of the clock connector.

Is the resistance as specified?

0 ohms

Go to Step 13

Go to Step 15

13

Measure the resistance between terminal 67 of the SDM and ground.

Is the resistance as specified?

Go to Step 14

Go to Step 15

14

Replace the SDM.

Did you complete the replacement?

--

Go to Step 16

--

15

Repair the wiring between the terminal 67 of the SDM and the clock.

Did you complete the repair?

--

Go to Step 16

--

16

  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