GM Service Manual Online
For 1990-2009 cars only

Circuit Description

During the Initiator Assembly Resistance test, the supplemental restraint Diagnostic Energy Reserve Module (DERM) grounds the Driver Side Low terminal B8 and turns on the driver current source at the Driver Side High terminal B9. During this test, the DERM monitors the voltage at the Driver Side Low and the difference between the Driver Side High and the Driver Side Low. When the values measure outside the expected range, the DERM sets the DTC B1028.

Conditions for Setting the DTC

The DTC sets when the voltage at the Driver Side Low measures below a specified value while its initiator resistance measures in a range above a specified value. This test runs once each ignition cycle during the Initiator Assembly Resistance test when:

    • No higher priority faults are detected during the Turn On test
    • No higher priority faults are detected during the Continuous Monitoring tests for one second
    • No Crank signal is present
    • Ignition 1 voltage measures above a specified value

Action Taken When the DTC Sets

The DERM turns on the AIR BAG warning lamp and sets a diagnostic trouble code.

Conditions for Clearing the DTC

The DTC clears when the ignition switch is turned OFF.

Diagnostic Aids

During the Initiator Assembly Resistance test, the DERM checks for the proper resistance of the following items:

    • The CKT 347
    • The CKT 348
    • The supplemental restraint steering wheel module coil
    • The supplemental restraint steering wheel inflator module

This test causes a known amount of current through a known amount of resistance causing a known amount of voltage at the Driver Side Low. When the measure resistance is in range and the voltage at the Driver Side Low measures too high or too low, the DERM sets the DTC.

Test Description

When measurements are requested in this chart use J 39200 Digital Multimeter with correct terminal adapter from J 35616 Connector Test Adapter Kit. When a check for proper connection is requested, refer to Intermittents and Poor Connections in Section 8A4. When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair.

DTC B1028- Current Sink or Source Failure

Step

Action

Value

Yes

No

1

Was the SRS Diagnostic System Check performed?

 

Go to Step 2

Go to SRS Diagnostic System Check

2

Replace the DERM. Refer to Supl Rst Diagnostic Energy Reserve Module .

Has the DERM been replaced?

 

Go to SRS Diagnostic System Check