Chevrolet Silverado / GMC Sierra. Manual — part 2911

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 AWD indicator control circuit will cause the AWD indicator to remain
on at all times. An open or high resistance will cause the AWD indicator to be inoperative during
the 2 second bulb check.

Circuit/System Testing

Check the interior dimming circuit pin 2 at the transfer case shift control switch for voltage for
the 2 seconds after turning the ignition on during the bulb check.

If less than battery voltage check the interior dimming circuit for an open or high resistance.
If the voltage is low or non existence and the circuit tests good replace the BCM. If the
interior dimming circuit and BCM test good go to the next step.

If the AWD indicator is on at all times check the AWD indicator control circuit for a short
to ground. If the AWD indicator is inoperative during bulb check, check the AWD indicator
control circuit for an open or high resistance or short to voltage. If the circuit checks good
continue to the next step.

With the ignition on shift the transmission to neutral and using transfer case output controls
attempt to command the AWD indicator off and on. If the AWD indicator is still inoperative
short to AWD indicator to ground, if the AWD indicator lights replace the module. If the
AWD indicator is still inoperative replace the switch.

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.

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

DTC B0775

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 B0775 01

4 High Indicator Circuit Short to Battery

DTC B0775 06

4 High Indicator Circuit Short to Ground or Open

Diagnostic Fault Information

Circuit/System Description

The 4 high indicator circuit consists of an indicator lamp feed circuit and an 4 high indicator lamp
control circuit. When the 4 high mode has been selected, current is supplied to the 4 high
indicator lamp by the interior lights dimming circuit, traveling through the 4 high indicator lamp
LED, at which time the transfer case shift control module supplies the ground through the 4 high
indicator lamp control circuit.

Conditions for Running the DTC

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

4 High Indicator Circuit

DTC B0775

06

DTC B0775

06

DTC B0775
01

-

2008 Chevrolet Silverado 1500

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

Silverado

The ignition is ON.

System voltage is 10-18 volts.

Conditions for Setting the DTC

The system monitors the voltage on the 4 high indicator control circuit.

If the system detects a voltage of 2 volts or less for 1.5 seconds when the 4 high indicator is
not commanded, the DTC is logged.

If the system detects a voltage of 4.5 volts or more when the 4 high indicator is commanded,
the DTC is logged.

Action Taken When the DTC Sets

The SERVICE 4WD indicator is not commanded on for this DTC.

Conditions for Clearing the DTC

The transfer case shift control module clears the DTC if the condition for setting the DTC is
not currently present.

A history DTC clears after 40 consecutive warm up cycles without a fault present.

History DTCs can be cleared using a scan tool.

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

2008 Chevrolet Silverado 1500

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

Silverado