Chevrolet Silverado / GMC Sierra. Manual — part 2916

The transfer case shift control module controls the transfer case lock solenoid.

The transfer case lock solenoid is released by being energized. This is accomplished by grounding
the lock solenoid control circuit during gears shifts, and in the AUTO 4WD mode. Locking action
is applied when power or ground are taken away from the lock solenoid, the transfer case motor
is prevented from moving. The system is capable of providing a 2HI, 4HI and 4LO lock-up
without the need of additional vehicle power to hold the transfer case in these positions.

This DTC detects an open lock solenoid coil, open motor lock control circuit, or an open batter
positive voltage circuit, or a short to voltage or ground on the lock solenoid control circuit.

Conditions for Running the DTC

The ignition is ON.

System voltage is 10.5-18 volts.

Conditions for Setting the DTC

The transfer case shift control module tries to unapply, turn OFF the lock solenoid by
grounding the motor control circuit.

If the module does not sense the battery voltage at the motor lock control circuit prior to
applying the motor lock, the DTC sets.

Transfer Case Lock control reads back as a high voltage when a low voltage is expected.

Action Taken When the DTC Sets

All shifting is disabled for failure types 01 and 04, normal shifting can occur for failure
types 02 and 08.

The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition
cycle.

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

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

When the circuits operating the lock solenoid are not complete the lock is engaged. When the
circuit is completed the lock is disengaged.

Circuit/System Testing

The battery positive voltage circuit and the lock solenoid control circuit must be tested for opens,
shorts to ground, shorts to voltage, and high resistance. This can also result from a electrically
faulted solenoid.

1. With the ignition on check which DTC is set. If DTC C0321 is set with failure type byte 04

then do the following.

The transfer case lock is unable to hold during a hold test and the transfer case actuator
will need to be replaced, and the motor learn procedure performed. If this is not the
case continue to the next step.

2. Disconnect the transfer case actuator, turn on the ignition and with a DMM check the

battery positive voltage circuit for battery voltage at the transfer case actuator.

If battery voltage is not seen then repair the battery positive voltage circuit for an open
or high resistance. If the circuit checks out proceed to the next step.

3. Disconnect the transfer case control module connector X2 and check the circuit for an open,

high resistance, short to ground, or short to voltage. If condition is found repair the circuit

2008 Chevrolet Silverado 1500

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

Silverado

or inline connector 109 as necessary, if the condition is not found refer to component
testing.

Component Testing

With the ignition off check the resistance of the lock solenoid with a DMM by probing Pins C
and B on the transfer case actuator.

If the resistance reads 16-42 ohms then replace the transfer case control module, program,
and complete the motor learn procedure. If the resistance is not in range then replace the
transfer case actuator, and complete the motor learn procedure.

Repair Procedures

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 Two/Four Wheel Drive Actuator Position Sensor Replacement

DTC C0374

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 C0374 54

General System Performance Temperature High

Diagnostic Fault Information

Circuit/System Description

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Invalid

General System Performance

C0374 54

-

-

-

2008 Chevrolet Silverado 1500

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

Silverado

The general system performance DTC sets based on a thermal module within the transfer case
shift control module software. The components included in this thermal model are the motor
driver within the transfer case shift control module, the shift motor, and the clutch inside the
transfer case.

The General System Performance includes the following components:

The transfer case shift control module

The transfer case clutch

The transfer case shift motor

This fault occurs when one of the three components included in the thermal model surpass the
upper limits of this model indicating possible damage to the transfer case or other driveline
components. This DTC detects an over temperature condition base on a thermal model.

Conditions for Running the DTC

The ignition is ON.

System voltage is 10.5-18 volts.

DTC C0896 is not set.

Conditions for Setting the DTC

This DTC sets if one of three components: motor driver inside the transfer case shift control
module, transfer case clutch, or the shift motor, exceed the thermal model within the software for
the module.

Action Taken When the DTC Sets

All range and mode changes will be disabled while the DTC is current.

The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition
cycle.

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 and current DTCs can be cleared using a scan tool.

Reference Information

2008 Chevrolet Silverado 1500

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

Silverado