Chevrolet Silverado / GMC Sierra. Service manual — part 660

a DTC will set. When the sensing and diagnostic module (SDM) detects this DTC within the
PPS, it will notify the customer of the enable/disable status by turning ON the OFF indicator on
the PASSENGER AIR BAG ON/OFF indicators. Then the PPS will communicate to the SDM
through serial data communications that a PPS fault is present. The SDM will then suppress the
deployment of the instrument panel (I/P) module and then turn the AIR BAG indicator ON.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

The PPS detects the voltage at the PPS sensor signal is less than 0.5 volt or greater than 4.5
volts for 500 milliseconds.

The PPS detects the voltage at the PPS sensor 5 volt reference is less than 4.5 volts or
greater than 9.1 volts for 500 milliseconds.

The PPS detects the amperage at the PPS sensor low reference is 25 mA or greater for 500
milliseconds.

Action Taken When the DTC Sets

The PPS will set a DTC, and then communicate with the SDM.

The SDM disables the I/P module deployment loop.

The PPS will turn on the passenger air bag status OFF indicator.

The SDM commands the AIR BAG indicator ON.

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

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Circuit/System Testing

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

1. Ignition OFF, disconnect the harness connector at the PPS pressure sensor and inspect the

component and harness sides for damage or corrosion.

If damage or corrosion is found, repair or replace as necessary.

2. Ignition ON, test for 4.5-5.5 volts between the voltage reference circuit terminal A and

ground.

If less that the specified range, test the voltage reference circuit for open/high
resistance or a short to ground. If the circuit tests normal, replace the PPS.

If greater that the specified range, test the voltage reference circuit for a short to
voltage. If the circuit tests normal, replace the PPS.

3. Ignition OFF, remove the AIR BAG BATT Fuse. Test for less than 2.0 ohms between low

reference terminal C and ground.

If greater than the specified range, test the low reference circuit for open/high
resistance. If the circuit tests normal, replace the PPS.

4. Ignition OFF, disconnect the harness connector at the PPS module.

5. Test for infinite resistance between the signal circuit terminal B and ground.

If less than the specified value, test the signal circuit for a short to ground.

6. Ignition ON, test for less than 1 volt between the signal circuit terminal B and ground.

If greater than the specified range, test the signal circuit for a short to voltage.

IMPORTANT:

The PPS pressure sensor is not serviced separately. The
PPS replacement with the PPS pressure sensor must be
serviced as a complete unit.

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

The PPS pressure sensor

The PPS module

The PPS pressure sensor wiring harness connector

The PPS module wiring harness connector

IMPORTANT: The AIR BAG BATT Fuse that supplies B+ voltage must be

removed to ensure the PPS module is inactive. An active PPS
module may cause inaccurate resistance readings.

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

7. Test for less than 1 ohm in the signal circuit between PPS module terminal 6 and PPS sensor

terminal B.

If greater than the specified range, test the signal circuit for open/high resistance. If the
circuit tests normal, replace the PPS.

8. If all circuits test normal, replace the PPS which includes the pressure sensor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

SIR/SRS Wiring Repairs

Control Module References for PPS replacement, setup, and programming

DTC B0079

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 Descriptors

DTC B0079 01

LF Seat Position Sensor Circuit Short to Battery

DTC B0079 02

LF Seat Position Sensor Circuit Short to Ground

DTC B0079 04

LF Seat Position Sensor Circuit Open

DTC B0079 06

LF Seat Position Sensor Circuit Short to Ground or Open Circuit

DTC B0079 08

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

LF Seat Position Sensor Circuit Signal Invalid

Diagnostic Fault Information

Circuit/System Description

The inflatable restraint seat position sensor (SPS) is used to determine the proximity of a front
driver or passenger seat position with respect to the frontal air bag. The SPS interfaces with the
sensing and diagnostic module (SDM). The state of the SPS allows the SDM to disable stage 2 of
the frontal air bag for a front seat that is forward of a forward/rearward point in seat track travel.
The SPS is a hall effect sensor that is mounted on the inboard seat track of the driver and
passenger seats. The seat track includes a metal bracket that shunts the SPS magnetic circuit
creating 2 states of seat position. The shunted state represents a rearward seat position. The non-
shunted state represents a forward position. The SPS provides 2 current ranges, one range for the
shunted state and a second range for a non-shunted state. These 2 states are inputs to the SDM,
state 1 (shunted) being the rearward threshold and state 2 (non-shunted) being the forward
threshold. When the SDM receives input from a SPS that state 1 threshold is reached (seat is
rearward), the SDM will not disable stage 2 deployment, if required by the deployment sensors.
When state 2 threshold is reached (seat is forward), the SDM will disable stage 2 deployment on
the side the seat is forward. The SDM monitors the SPS circuit and if a fault is detected, the
SDM will set codes B0079 and defaults to disabling stage 2 frontal deployment.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

B0079 01

The SDM detects the SPS circuit is shorted to voltage for 500 milliseconds.

B0079 06

The SDM detects the SPS circuit is shorted to ground or an open occur for 500 milliseconds.

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Signal

Performance

Seat Position Sensor Left
Low Reference

B0079 02,

06

B0079 04 B0079 04 B0079 01

B0079 08

Seat Position Sensor Left
Signal

B0079 02,

06

B0079 04 B0079 04 B0079 01

B0079 08

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado