Chevrolet Silverado / GMC Sierra. Manual — part 2873

Circuit/System Description

The transfer case control module commands shifts through motor A and motor B control circuits
causing the transfer actuator to shift the transfer case to different modes or ranges depending on
driver selection. The transfer case control module monitors actuator current and incremental
sensor output in order to shift the transfer case and verify that the proper position has been
obtained. Deviations in current and position from expected values will cause this DTC to set.

Conditions for Running the DTC

The ignition is ON.

System voltage is 10.5-18 volts.

Conditions for Setting the DTC

A shift request was received but could not be completed within 15 seconds causing this
DTC to set.

An incomplete shift is one that cannot reach the desired mode or range and cannot return to
the original mode or range.

If the shift lever detent shaft were to bind, or there was a mechanical failure, or motor A
control and motor B control were shorted together the shift would not be completed. This
will cause the DTC to set in order to protect the system components from damage.

A faulty transfer case shift control module can cause incorrect incremental sensor or motor
current measurements which would also result in this DTC setting.

Intermittent motor A/B or incremental sensor circuit wiring failures can also cause this DTC
to set.

Action Taken When the DTC Sets

All shifting is disabled until condition is corrected.

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

DTC C0569 4B is set.

Conditions for Clearing the DTC

The transfer case shift control module clears the DTC if the condition for setting the DTC is

Circuit

Ground

Resistance

Voltage

Timeout

Unable to Complete Shift

-

-

-

DTC C0387 59

2008 Chevrolet Silverado 1500

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

Silverado

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

Control Module References for scan tool information

Diagnostic Aids

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

Circuit/System Testing

1. If either DTC C0306 or DTC C0396 is set, diagnose these DTCs first.

2. Using a DMM, with the Ignition off, check to see if motor A control and motor B control

are shorted together after disconnecting the transfer case control module and the transfer
case actuator.

If motor A control is shorted to motor B control repair the circuits as necessary. If the
circuits checked good go to next step.

3. Inspect the actuator connector for damage or corrosion.

If corrosion is found then repair the damage and attempt an ATC motor learn
procedure. If unable to complete motor learn go to next step.

2008 Chevrolet Silverado 1500

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

Silverado

4. Replace the transfer case shift control module with known good unit and attempt an ATC

motor learn.

If the ATC motor learn is successful then system is OK, if not then proceed to next
step.

5. Remove the transfer actuator and check to see if the shift detent shaft is binding.

If the shift lever detent shaft is binding refer to Transfer Case Disassemble. If the
shift lever detent shaft is not binding replace the transfer case actuator.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Transfer Case Two/Four Wheel Drive Actuator Replacement

Transfer Case Disassemble

DTC C0396

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 C0396 01

Incremental Position Sensor Circuit Short to Battery

DTC C0396 02

Incremental Position Sensor Circuit Short to Ground

DTC C0396 04

Incremental Position Sensor Open Circuit

DTC C0396 05

Incremental Position Sensor Circuit Short to Battery or Open

2008 Chevrolet Silverado 1500

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

Silverado

Diagnostic Fault Information

Circuit/System Description

The transfer case shift control module has an input from incremental sensor which shows the
speed, transfer case range, and direction of the transfer case mode or range shifts. The incremental
sensor is an integral part of the transfer case actuator and can not be replaced independently. The
incremental sensor indicates important information about the speed and direction of the transfer
case two/four wheel drive actuator position. This sensor receives an 8-volt reference signal from
the transfer case control module and gets this data back via the transfer case incremental impulse
signal, as well as the incremental direction signal in order to know the current location.

Conditions for Running the DTC

The ignition is ON.

System voltage is 10.5-18 volts.

Conditions for Setting the DTC

The transfer case control module sees a incremental 8-volt reference signal that is not
between 1.5-8.2 volts indicating a short to ground or open if low and a short to voltage if
high.

The module does not receive a incremental impulse signal voltage between 0.5-4.6 volts.

The incremental low reference circuit has an open or high resistance.

Action Taken When the DTC Sets

All shifting is disabled until the condition no longer exists.

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

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Invalid

Incremental Position Sensor
Circuit

DTC C0396

02

DTC C0396

04

DTC C0396

05

DTC C0396
01
DTC C0396
05

-

2008 Chevrolet Silverado 1500

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

Silverado