Content .. 2877 2878 2879 2880 ..
Chevrolet Silverado / GMC Sierra. Manual - part 2879
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The indicator circuits consists of an interior lights dimming circuit and an indicator control
circuit. When a mode has been selected, current is supplied to the indicator by the interior lights
dimming circuit, traveling through the indicator LED, at which time the transfer case shift control
module supplies the ground through the indicator lamp control circuit.
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Scan Tool Data List
Scan Tool Data Definitions
Diagnostic Aids
A short to ground on the indicator control circuit will cause the indicator to remain on at all
times.
Circuit/System Testing
1. With in ignition off disconnect connector X1 at the transfer case control module and turn the
ignition on. With a jumper wire probe the indicator control circuit of the affected indicator
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
and take the other end of the jumper to ground. If the indicator comes on then replace the
transfer case control module, program, and perform the motor learn procedure.
2. If the affected indicator did not come on then check the indicator control circuit for an open
or high resistance. If the circuit checks good then replace the transfer case shift control
switch.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Transfer Case Shift Control Switch Replacement (Without SLT) or Transfer Case
Shift Control Switch Replacement (With SLT)
Control Module References for TCSCM replacement, setup, and programming
Transfer Case High/Low Clutch Reset
SERVICE INDICATOR ALWAYS ON
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.
Circuit/System Description
If the service indicator needs to be turned on the transfer case shift control module sends a signal
via LAN to the instrument panel asking the I/P to command the Service 4WD indicator.
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Circuit Testing
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Scan Tool Data List
Scan Tool Data Definitions
Circuit/System Testing
1. If the Service 4WD indicator is on and there are no DTCs check the fuse for the transfer
case as this would cause the transfer case control module to drop off the LAN causing a
service indicator.
2. If the fuse is good check the module power and grounds for proper connections as this could
cause the same thing as a blown fuse.
3. If this checks OK then check all other U codes that may be set against the transfer case shift
control module such as I/P, BCM, PCM, and follow the proper U code diagnostic.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Transfer Case Shift Control Switch Replacement (Without SLT) or Transfer Case
Shift Control Switch Replacement (With SLT)
Control Module References for TCSCM replacement, setup, and programming
Transfer Case High/Low Clutch Reset
TRANSFER CASE HIGH/LOW CLUTCH RESET
Using a Scan Tool
1. Turn the ignition on. Go to the special functions heading in the scan tool.
2. Select Clutch Reset Procedure (Motor Learn Procedure).
3. When the Clutch Reset Procedure is initiated you should hear the motor engage, indicating a
successful learn procedure.
Using the Transfer Case Shift Control Switch
1. Turn the ignition to accessory, place the switch into the 2 high mode.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
2. Turn the switch clockwise past 4 low into the neutral request mode and hold for 30 seconds.
3. An audible noise from the motor should occur indicating a successful learn procedure.
TRANSFER CASE POPPING NOISE
TRANSFER CASE WHINE OR RUMBLE NOISE
TRANSFER CASE GROWL OR GRINDING NOISE
Cause
Correction
DEFINITION: A faulty internal transfer case component that causes a popping noise in the
transfer case.
Review the Symptoms - Transfer Case and perform the necessary inspections.
Chain jump
Replace the chain and sprockets. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Replace the shaft bearings. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Inspect for damaged components caused by metal debris.
Refer to Drive Chain, Drive Sprocket, and Driven
Sprocket Cleaning and Inspection and Front Output
Shaft and Input Shaft Cleaning and Inspection.
Cause
Correction
DEFINITION: A faulty internal transfer case component that causes a whine or rumbling
noise in the transfer case.
Review the Symptoms - Transfer Case and perform the necessary inspections.
Faulty bearings
1. Inspect all of the bearings and journals. Refer to Rear
Output Shaft Cleaning and Inspection, Front
Output Shaft and Input Shaft Cleaning and
Inspection, and Drive Chain, Drive Sprocket, and
Driven Sprocket Cleaning and Inspection.
2. Replace any faulty bearings and any components with
faulty bearing journals. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Cause
Correction
DEFINITION: A faulty internal transfer case component that causes a growl or grinding
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Content .. 2877 2878 2879 2880 ..