Chevrolet Silverado / GMC Sierra. Service manual — part 658

Circuit/System Description

The inflatable restraint seat belt tension sensor is a 3-wire potentiometer mounted on the buckle
side of the passenger seat belt and provides an input to the passenger presence system (PPS).
When an infant car seat is properly restrained on the front passenger seat, the seat belt is tightly
secured through the car seat. The seat belt pulls on the tension sensor and changes the voltage
signal to the PPS module. The PPS monitors the belt tension sensor signal circuit and if a fault is
detected, DTC will be set. When the PPS detects this DTC it will send out a serial data message
and the SDM will notify the customer of the enable/disable status by turning on the OFF
indicator on the PASSENGER AIR BAG ON/OFF indicators. The SDM will then suppress the
deployment of the instrument panel (I/P) module and 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 belt tension sensor signal circuit is less than 0.5 volt or
greater than 4.5 volts for 500 milliseconds.

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

The PPS detects the amperage at the belt tension sensor low reference circuit 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.

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Belt Tension Sensor Voltage
Reference

B0071 03

B0071 03

B0071 03

-

Belt Tension Sensor Low
Reference

-

B0071 07

B0071 07

-

Belt Tension Sensor Signal

B0071 03

B0071 03, 07 B0071 03, 07

B0071 07

2008 Chevrolet Silverado 1500

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

Silverado

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.

Diagnostic Aids

Inspect the passenger seat belt tension sensor signal, voltage reference, and low reference circuits
carefully for cutting and/or chafing.

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 Testing

IMPORTANT: The seat belt tension sensor is not serviced separately. The seat

belt buckle replacement with the seat belt tension sensor must be
serviced as a complete unit.
When removing connectors, inspect for damage or corrosion.

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 seat belt tension 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 B 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 in the underhood fuse block. Test for less

than 2.0 ohms between low reference terminal A and ground.

If greater than specified, 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. Ignition ON, test for infinite resistance between the signal circuit terminal C and ground.

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

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

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

7. Test for less than 1 ohm in the signal circuit between the PPS module terminal 4 and the belt

tension sensor terminal C

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

8. If all circuits test normal, replace the passenger seat belt buckle which includes the seat belt

Damage or corrosion in the following requires repair or
replacement of the affected component/connector:

The seat belt tension sensor

The PPS module

The seat belt tension sensor wiring harness connector

The PPS module wiring harness connector

IMPORTANT: The AIR BAG BATT Fuse 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

tension sensor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Front Seat Belt Buckle Replacement

SIR/SRS Wiring Repairs

Control Module References for PPS replacement, setup, and programming

DTC B0072 OR B0073

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 B0072 01

LF Seat Belt Sensor Circuit Short to Battery

DTC B0072 02

LF Seat Belt Sensor Circuit Short to Ground

DTC B0072 04

LF Seat Belt Sensor Circuit Open Circuit

DTC B0072 06

LF Seat Belt Sensor Circuit Short To Ground or Open Circuit

DTC B0072 08

LF Seat Belt Sensor Circuit Signal Invalid

DTC B0073 01

2008 Chevrolet Silverado 1500

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

Silverado