GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B1378 : LF Side Deployment Loop Resistance Above Threshold

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

LF Side Module High Circuit

B1380

B1378

B1378

B1381

B1379

LF Side Module Low Circuit

B1380

B1378

B1378

B1381

B1379

Circuit/System Description

If a malfunction is detected, a DTC will be stored in non-volatile memory. During a side or frontal crash of sufficient force the inflatable restraint sensing and diagnostic module (SDM) will allow current to flow through the deployment loop in order to deploy the LF side module. The SDM performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. A shorting bar used within the LF side module connector which will short together both LF side module high and low circuits when the connector is disconnected. This will help to prevent unwanted deployment of the inflator module during servicing.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

The LF side module deployment loop resistance is more than 3.54 ohms.

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.
    • A history DTC will clear once 255 malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

SIR Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Circuit/System Testing

    Important: When removing connectors inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector.

       • The side module
       • The SDM module
       • The SDM wiring harness connector

  1. Ignition OFF, disconnect LF side module in-line connector.
  2. Disconnect the SDM connector. Refer to SDM replacement in Repair Instructions for connector location.
  3. Test the high and low circuits between the SDM and LF side module for a open/high resistance. Verify that a open/high resistance does not exist.
  4. If the above condition is found make the appropriate repair.
  5. If all circuits test normal then replace the SDM.
  6. Ignition ON, use a scan tool to observe the SIR DTC display. Verify DTC B1378 is set current.
  7. Replace the LF side module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Inflatable Restraint Roof Side Rail Module Replacement
    •  Control Module References for SDM replacement, setup, and programming