Chevrolet Silverado / GMC Sierra. Service manual — part 2927

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
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.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

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

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

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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.

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

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

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

TRANSFER CASE GROWL OR GRINDING NOISE

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
noise in the transfer case while the vehicle is turning or in a four wheel drive mode.
Review the Symptoms - Transfer Case and perform the necessary inspections.

High/low planetary carrier
assembly

1. Inspect the high/low planetary carrier assembly for the

following conditions:

Chipped, bent, or deformed teeth

Planetary gear needle bearings worn

Planetary gear thrust washers cracked or missing

Seized or binding planetary gears

Refer to High/Low Planetary Carrier Cleaning
and Inspection .

2. Replace the high/low planetary carrier assembly if any of

the above conditions exist. Refer to Transfer Case
Disassemble and Transfer Case Assemble.

1. Inspect the input shaft in the planetary carrier assembly

for excessive thrust end play.

2. Inspect the input shaft teeth for the following conditions:

Damage

Worn or galled thrust surfaces

Excessive wear

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado