Chevrolet Silverado / GMC Sierra. Manual — part 2920

Circuit/System Testing

The incremental sensor impulse signal circuit, incremental direction signal circuit, incremental
sensor low reference circuit, and the 8-volt reference circuit will need to be check for a short to
ground, open, high resistance, and a short to voltage using the following steps.

1. Disconnect the connector at the transfer case actuator and check the 8-volt reference signal

on pin G at the transfer case actuator with a DMM, ignition on, the voltage should read 7.8-
8.2 volts.

If the voltage does not read within the specifications then check the 8-volt reference
circuit for a short to voltage, open, high resistance, or short to ground. If the circuit
checks good and the voltage is out of range replace the transfer case control module,
program, and perform the motor learn procedure. If the circuit checks good continue
to next step.

2. At the transfer case actuator, with a jumper harness short the 8-volt reference circuit pin G

to the incremental impulse signal pin E and note the voltage on the scan tool data display.

If the voltage does not read 7.8-8.2 volts check the incremental impulse signal circuit
for and open, high resistance, short to ground, or short to voltage. If the circuit checks
good then go to the next step.

3. Check the incremental direction circuit for an open, short to ground, high resistance, or a

short to voltage by probing pin F at the transfer case actuator and pin 14 and transfer case
control module connector X2.

If all circuit test good replace the transfer case actuator and perform 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 Replacement

DTC C0397

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.

DTC Descriptor

DTC C0397 64

Transfer Case Clutch Performance Actuator Slipping

Diagnostic Fault Information

Circuit/System Description

The transfer case in the Auto 4WD mode attempts to correct for slip by monitoring the front and
rear wheel speed sensors. If the transfer case is unable to correct for slip when there is a
difference between the front and rear speed sensors the transfer case will apply the clutch. If the
transfer case in unable to correct this slip and the clutch begins to heat up based on a thermal
model inside the transfer case control module this DTC will be set.

Conditions for Running the DTC

The ignition is ON.

System voltage is 10.5-18 volts.

Conditions for Setting the DTC

The transfer case is unable to correct slip due to a clutch overheat condition as a result in
surpassing the thermal model that is stored in the transfer case control module.

Action Taken When the DTC Sets

Shifting is still possible but in a reduced capacity which may cause undesirable slip
correction events.

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

Conditions for Clearing the DTC

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Actuator

Slipping

Transfer Case Clutch
Performance

-

-

-

DTC C0397

64

2008 Chevrolet Silverado 1500

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

Silverado

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

Scan Tool Data List

Scan Tool Data Definitions

Diagnostic Aids

Motor control A shorting to motor control B could cause this DTC.

Circuit/System Testing

Check for EBCM DTCs as an incorrect speed sensor reading could cause this issue. If no other
DTCs are found then refer to Transfer Case Disassemble to inspect for possible clutch damage.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Transfer Case Disassemble

2008 Chevrolet Silverado 1500

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

Silverado