Chevrolet Silverado / GMC Sierra. Service manual — part 659

RF Seat Belt Sensor Circuit Short to Battery

DTC B0073 02

RF Seat Belt Sensor Circuit Short to Ground

DTC B0073 04

RF Seat Belt Sensor Circuit Open Circuit

DTC B0073 06

RF Seat Belt Sensor Circuit Short To Ground or Open Circuit

DTC B0073 08

RF Seat Belt Sensor Circuit Signal Invalid

Diagnostic Fault Information

Circuit/System Description

The inflatable restraint seat belt switch is within the seat belt retractor and provides an input to
the inflatable restraint sensing and diagnostic module (SDM). The SDM supplies a low reference
circuit and a seat belt switch signal circuit to determine a buckled or unbuckled condition. The
SDM monitors the seat belt switch circuits, and if a fault is detected a DTC will be set.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Signal

Performance

Seat Position Sensor Low
Reference

-

B0072 04,

B0073 04

B0072 04 B0079 01

B0072 08

Seat Belt Switch Left Signal

B0073 02,

06

B0072 04 B0072 04 B0072 01

B0072 08

Seat Belt Switch Right Signal

B0073 02,

06

B0073 04 B0073 04 B0073 01

B0073 08

2008 Chevrolet Silverado 1500

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

Silverado

B0072 01, B0073 01

The SDM detects the seat switch signal circuit or low reference circuit is shorted to voltage for
500 milliseconds.

B0072 02, B0073 02

The SDM detects the seat switch signal circuit or low reference circuit is shorted to ground for
500 milliseconds.

B0072 04, B0073 04

The SDM detects the seat switch signal circuit or low reference circuit is open for 500
milliseconds.

B0072 06, B0073 06

The SDM detects the seat switch signal circuit or low reference circuit is shorted to ground or an
open for 500 milliseconds.

B0072 08, B0073 08

The SDM detects an invalid signal in the seat switch signal circuit.

Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON.

The SDM will store a DTC.

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

Seat Belt Schematics

Connector End View Reference

Component Connector End Views

2008 Chevrolet Silverado 1500

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

Silverado

Electrical Information Reference

Circuit Testing

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Connector Repairs

Circuit/System Testing

1. Ignition OFF, disconnect the seat belt switch connector.

2. Test for less than 1.0 ohm between low reference terminal B and ground.

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

3. Ignition ON. Test for 1.0 - 1.6 volts between the signal circuit terminal A and ground.

If less that the specified range, test the signal circuit for 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.

4. If the circuits test normal, replace the seat belt retractor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Seat Belt Retractor Pretensioner Replacement - Front (Regular Cab) or Seat Belt
Retractor Pretensioner Replacement - Front (Extended Cab) or Seat Belt Retractor
Pretensioner Replacement - Front (Crew Cab)

IMPORTANT:

The seat belt switch is not serviced separately. The seat belt
retractor with the seat belt switch 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 SDM module

The seat belt switch wiring harness connector

The seat belt switch

The SDM wiring harness connector

2008 Chevrolet Silverado 1500

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

Silverado

SIR/SRS Wiring Repairs

Control Module References for SDM and PPS replacement, setup, and programming

DTC B0074

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 B0074 03

Passenger Occupant Classification Sensor Circuit Voltage Below Threshold

DTC B0074 07

Passenger Occupant Classification Circuit Voltage Above Threshold

DTC B0074 08

Passenger Occupant Classification Circuit Signal Invalid

Diagnostic Fault Information

Circuit/System Description

The passenger presence system (PPS) uses a silicone filled sensor pad located underneath the
passenger seat foam cushion and is connected by a hose clamp to a pressure sensor. The weight of
the occupant sitting in the front passenger seat is measured as a pressure change within the
bladder by the pressure sensor. The pressure sensor is a 3-wire sensor consisting of a power,
ground, and signal circuit. The PPS continually monitors itself and if a fault in this circuit occurs,

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Pressure Sensor Low Reference

-

B0074 03

B0074 03

-

Pressure Sensor Signal

B0074 07

B0074 03, 07 B0074 03, 07

B0074 03

Pressure Sensor Voltage
Reference

B0074 07

B0074 07

B0074 07

B0074 03

2008 Chevrolet Silverado 1500

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

Silverado