Chevrolet Silverado / GMC Sierra. Service manual — part 2879

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 the ignition off disconnect connector X1 at the transfer case control module and turn

the 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.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

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