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Chevrolet Silverado / GMC Sierra. Manual - part 2293
2008 ACCESSORIES & EQUIPMENT
Horns - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
SPECIFICATIONS
FASTENER TIGHTENING SPECIFICATIONS
SCHEMATIC AND ROUTING DIAGRAMS
HORN SCHEMATICS
Fig. 1: Horn Schematic
Courtesy of GENERAL MOTORS CORP.
DIAGNOSTIC INFORMATION AND PROCEDURES
Application
Specification
Metric
English
Horn Bolt
9 N.m
80 lb in
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Horns - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Horns - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
DIAGNOSTIC CODE INDEX
DIAGNOSTIC CODE INDEX
DIAGNOSTIC STARTING POINT - HORNS
Begin the system diagnosis with the Diagnostic System Check - Vehicle . The Diagnostic
System Check will provide the following information:
The identification of the control modules which command the system
The ability of the control modules to communicate through the serial data circuit
The identification of any stored diagnostic trouble codes (DTCs) and their status
The use of the Diagnostic System Check will identify the correct procedure for diagnosing the
system and where the procedure is located.
DTC B2750
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 Descriptor
DTC B2750 00
Horn Relay Coil Circuit
Diagnostic Fault Information
DTC
Description
DTC B2750
B2750 00: Horn Relay Coil Circuit
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
Horn Relay Control
B2750 00
B2750 00
B2750 00
-
Horn Control
2
2
1
-
Horn Switch Ground
-
2
2
-
Horn Ground
-
2
2
-
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Horns - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Circuit/System Description
The body control module (BCM) controls the horn relay by grounding the control circuit of the
horn relay coil energizing the relay. When the horn relay is energized, the horn relay contacts
close applying voltage through the horn fuse and the horn control circuit to the horns.
Conditions for Running the DTC
When the output is actively being requested by the BCM.
Conditions for Setting the DTC
The BCM detects a short to ground, open or short to battery in the horn relay control circuit for
approximately 125 milliseconds.
Action Taken When the DTC Sets
The BCM disables the output to the horn relay until the next ignition cycle.
Conditions for Clearing the DTC
The DTC clears when the fault is no longer detected.
The current DTC will become history when the request for the output is removed.
The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.
Reference Information
Schematic Reference
Horn Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Horns System Description and Operation
Electrical Information Reference
1. Horn Always On
2. Horn Inoperative
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Horns - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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
Command the horn ON and OFF with the scan tool. The horn should turn ON and OFF when
changing between the commanded states.
Circuit/System Testing
1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal G1 and B+.
3. Command the horn ON and OFF with a scan tool. The test lamp should turn ON and OFF
when changing between the commanded states.
If the test lamp is always OFF, test the control circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the BCM.
4. If all circuits test normal, replace the underhood fuse block.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Underhood Electrical Center or Junction Block Bracket Replacement
Control Module References for BCM replacement, setup and programming
SYMPTOMS - HORNS
IMPORTANT: The following steps must be completed before using the symptom
tables:
1. Perform Diagnostic System Check - Vehicle , before using
the symptom tables in order to verify that all of the following
are true:
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Horns - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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