Chevrolet Silverado / GMC Sierra. Service manual — part 2926

to 7.5 volts.

Circuit/System Testing

1. Review the scan tool data list mode switch selected and select difference mode with the

transfer case shift control switch. Does the mode switch selected parameter on the scan tool
change as you change modes on the switch?

2. If the modes change according to the scan tool replace the transfer case control module,

reprogram, complete the motor learn procedure. If the modes on the scan tool not change
replace the 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

NO CORRECTION FOR SLIP IN ALL-WHEEL DRIVE MODE

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

When transfer case is in auto 4WD mode the transfer case control module monitors the front
wheel speeds and the rear wheel speeds. When a noticeable difference between the front and rear
is seen the transfer case control module sends a PWM voltage to the motor so it can apply the
clutch in order to correct a slip condition. The slip conditions is the difference in speed between
the front and rear axles. The module has a thermal model based system so when the slip
correction can not be made when a large percentage PWM signal has been sent, it will disable the
system to prevent damage to the clutches.

Reference Information

Schematic Reference

2008 Chevrolet Silverado 1500

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

Silverado

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

Erratic wheel speed sensors can cause this condition to occur. Monitor the wheel speeds using the
EBCM scan tool data list.

Circuit/System Testing

1. Monitor the wheel speed sensors using the EMCM scan tool data list. If the wheel speeds

are erratic or there is a large difference between front and rear then diagnose and repair as
necessary. Check for EBCM DTCs as they have likely set for wheel speed performance.

2. If nothing is found with wheel speed performance then the clutches may be excessively

warn. Refer to Transfer Case Disassemble.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Transfer Case Disassemble

TRANSFER CASE SHIFT CONTROL SWITCH INDICATOR ALWAYS ON - TWO OR MORE

Diagnostic Instructions

2008 Chevrolet Silverado 1500

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

Silverado

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

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

2008 Chevrolet Silverado 1500

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

Silverado

ignition on. If the affected indicator goes out replace the transfer case control module,
program, and perform the motor learn procedure.

2. If the affected indicator did not go out check for a short to ground on the affected indicator

control circuit. If this checks as 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

TRANSFER CASE SHIFT CONTROL SWITCH INDICATOR INOPERATIVE - ONE OR MORE

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

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

2008 Chevrolet Silverado 1500

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

Silverado