GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

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

DTC Descriptors

DTC B0079 01: Driver Seat Position Sensor Circuit Short to Battery

DTC B0079 02: Driver Seat Position Sensor Circuit Short to Ground

DTC B0079 04: Driver Seat Position Sensor Circuit Open

DTC B0079 06: Driver Seat Position Sensor Circuit Short to Ground or Open Circuit

DTC B0079 08: Driver Seat Position Sensor Circuit Signal Invalid

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

LF Seat Position Sensor Signal

B0079 02, B0079 06

B0079 04, B0079 06

B0079 01

B0079 08

LF Seat Position Sensor Low Reference

B0079 02, B0079 06

B0079 04, B0079 06

B0079 01

B0079 08

RF Seat Position Sensor Signal

B0080 02, B0080 06

B0080 04, B0080 06

B0080 01

B0080 08

RF Seat Position Sensor Low Reference

B0080 02, B0080 06

B0080 04, B0080 06

B0080 01

B0080 08

Circuit/System Description

The seat position sensor is used to determine the proximity of a front driver seat position with respect to the inflatable restraint I/P module. The seat position sensor is a hall effect sensor that is mounted on the seat track of the front driver seat. The seat position sensor is connected to the sensing and diagnostic module (SDM) with a low reference and a signal circuit. The SDM uses the state of the seat position sensor to determine the need for a stage 2 deployment of the inflatable restraint I/P module. When the seat is in the forward position stage 2 deployment is disabled, and when in the rearward position stage 2 deployment is enabled. The SDM monitors the LF seat position sensor signal circuit and if a fault is detected, the SDM will set DTC B0079 and defaults to disabling stage 2 inflatable restraint I/P module deployment.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

B0079 01

The SDM detects the LF seat position sensor signal circuit is shorted to voltage for 500 milliseconds.

B0079 02

The SDM detects the LF seat position sensor signal circuit is shorted to ground for 500 milliseconds.

B0079 04

The SDM detects the LF seat position sensor signal circuit is open for 500 milliseconds.

B0079 06

The SDM detects the LF seat position sensor signal circuit is shorted to ground or an open for 500 milliseconds.

B0079 08

The SDM detects an invalid signal on the LF seat position sensor signal circuit.

Action Taken When the DTC Sets

    •  The SDM defaults the seat position sensor to seat forward threshold.
    • The SDM requests the instrument panel cluster (IPC) to illuminate the AIR BAG indicator.

Conditions for Clearing the DTC

    • The condition for setting the DTC no longer exists.
    • A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

SIR Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

SIR System Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the SDM Driver Seat Position Sensor parameter while moving the driver seat fully forward and fully rearward. The parameter should cycle between Forward to Rearward as the seat is moved in the respective direction and DTC B0079 should not set.

If the parameters are correct and DTC B0079 is set, replace the SDM.

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:

   • Seat position sensor
   • SDM
   • Seat position sensor wiring harness connector
   • SDM wiring harness connector

  1. Ignition OFF, disconnect the harness connector at the LF seat position sensor.
  2. Test for less than 10 ohms between low reference circuit terminal 1 and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the SDM.
  4. Ignition ON, test for 4.5-5.5 volts between the signal circuit terminal 2 and ground.
  5. If less that the specified range, test the signal circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the SDM.
    If greater that the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the SDM.
  6. If the circuits test normal, test or replace the seat position sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for SDM replacement, setup, and programming