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Chevrolet Silverado / GMC Sierra. Manual - part 2482
DTC B3884
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 B3884 00
Center High Mounted Stop Lamp (CHMSL) Circuit
Diagnostic Fault Information
Circuit/System Description
When the brake pedal is applied, the brake pedal switch normally closed contact signal circuit
voltage is interrupted to the body control module (BCM). Upon brake activation, the body
control module (BCM) applies voltage through the CHMSL relay control circuit to the coil side
of the relay. Ground is applied at all times to the other side of the CHMSL relay coil therefore
the relay is now energized. Battery voltage is then applied through the switch side of the relay,
the CHMSL fuse, and the CHMSL control circuit to the center high mounted stop lamp
(CHMSL). The CHMSL is grounded at G 200.
Conditions for Running the DTC
The ignition is ON.
The stop lamps must be commanded ON.
Conditions for Setting the DTC
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
CHMSL Relay Control
B3884 00
1
2
-
CHMSL Control
1
1
2
-
CHMSL Relay Control
-
1
-
-
CHMSL Ground
-
1
-
-
1. Center High Mounted Stop Lamp (CHMSL) Inoperative
2. Center High Mounted Stop Lamp (CHMSL) Always On
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The BCM detects a short to ground in the CHMSL relay control circuit when the stop lamps are
commanded ON.
Action Taken When the DTC Sets
The CHMSL does not illuminate.
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present.
A history DTC clears after 100 malfunction-free ignition cycles.
Reference Information
Schematic Reference
Exterior Lights Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Exterior Lighting Systems 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, press the brake pedal. The CHMSL should illuminate.
Circuit/System Testing
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
1. Ignition OFF, disconnect the harness connectors at the center high mounted stop lamp.
2. Test for less than 1.0 ohm of resistance between the ground circuit terminals B and ground.
If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the stop lamp control circuit terminals A and ground circuit
terminals B.
4. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF
when changing between the commanded states.
If the test lamp is always ON, test the control circuit for a short to voltage.
If the test lamp is always OFF, test the control circuit for a short to ground or an
open/high resistance.
5. If all circuits test normal, test or replace the center high mounted stop lamp.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Underhood Electrical Center or Junction Block Replacement
Control Module References for BCM replacement, setup, and programming
SYMPTOMS - LIGHTING
1. Perform the Diagnostic System Check - Vehicle , before using the Symptom Tables in
order to verify that all of the following are true:
There are no DTCs set.
The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions.
Refer to the following:
Exterior Lighting Systems Description and Operation
Interior Lighting Systems Description and Operation
Visual/Physical Inspection
Inspect for aftermarket devices which could affect the operation of the Lighting System.
Refer to Checking Aftermarket Accessories .
Inspect the easily accessible or visible system components for obvious damage or conditions
which could cause the symptom.
Intermittent
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to
Testing for Intermittent Conditions and Poor Connections .
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the
symptom:
Backup Lamps Malfunction
Courtesy Lamps Malfunction (w/AN3) or Courtesy Lamps Malfunction (w/o AN3)
Daytime Running Lamps Malfunction
Exterior Courtesy Lamps Malfunction
Front Fog Lamps Malfunction
Hazard Lamps Malfunction
Headlamps Malfunction
Headlamps Flash to Pass Inoperative
High Beam Indicator Malfunction
Interior Backlighting Malfunction (w/AN3) or Interior Backlighting Malfunction
(w/o AN3)
Park, License, and/or Tail Lamps Malfunction
Reading Lamps Malfunction
Stop Lamps Malfunction
Turn Signal Lamps and/or Indicators Malfunction
Vanity Mirror Lamp Malfunction
BACKUP LAMPS MALFUNCTION
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.
Diagnostic Fault Information
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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