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Chevrolet Silverado / GMC Sierra. Manual - part 2871
The 5-volt reference circuit and the switch signal will have to be checked for shorts to ground,
opens, high resistance, and shorts to voltage by following the below listed steps.
1. Reference the mode switch supply voltage with a scan tool.
The scan tool should indicate 4.8-5.2 volts. If the scan tool indicates the voltage is
within this specification then with a jumper wire short the switch signal circuit pin 12
on the switch to the 5-volt reference circuit pin 11 on the switch. If the mode switch
return voltage on the scan tool measures 4.8-5.2 volts then replace the switch.
2. If the mode switch return does not read 4.8-5.2 volts check the switch signal circuit and the
5-volt reference circuits for a short to ground, short to voltage, open, or high resistance.
If no shorts or high resistance are found on the switch signal or 5-volt reference
circuits then replace the transfer case shift control module, reprogram, and complete
the motor learn procedure.
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
DTC C0306
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 C0306 02
Motor A or B Circuit Short to Ground
DTC C0306 05
Motor A or B 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 motor is a bi-directional, permanent magnet, DC motor. When energized,
through motor control A or motor control B, the ground is provided by the opposing motor
control circuit and then grounded through the transfer case shift control module ground circuit,
the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift
the transfer case between the following modes or ranges:
2HI
4HI
4LO
Neutral
This DTC detects an open, short to voltage, or short to ground in the motor control A or motor
control B circuits, or an open, or short to ground inside the motor.
Conditions for Running the DTC
The ignition is ON.
System voltage is 10.5-18 volts.
Conditions for Setting the DTC
The system tests the motor circuits by checking for unwanted voltage.
Then, the system supplies voltage on each of the motor circuits and reads the voltage back
on the other circuit.
If the system detects a condition with the circuits, the DTC is logged. The transfer case shift
control module senses a low voltage return in the motor control A or motor control B
circuits when a high voltage is expected.
The fault must remain current for 30 seconds to set the DTC.
Action Taken When the DTC Sets
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
Motor A or B Circuit
DTC C0306
02
DTC C0306
05
DTC C0306
05
-
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
All shifting is disabled.
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
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
It is possible to have windings inside the motor shorted to the case resulting in a short to ground
causing this DTC to set.
Circuit/System Testing
The motor A control and motor B circuits need to be checked for shorts to ground, opens, high
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
resistance, and shorts to voltage by following the below listed steps.
1. With the ignition off disconnect connector X3 from the transfer case control module, and
also disconnect the connector at the transfer case actuator.
With a DMM check the motor A control and motor B control circuits for an open,
high resistance, or short to ground and repair as necessary. If all check good go to the
next step.
2. Connect X3 at the transfer case control module and turn on the ignition.
3. Check to motor A control and motor B control circuits for a short to voltage. If the circuits
shows to indication of a short to voltage go to component testing.
Component Testing
1. Turn the ignition off and check the motor windings for an internal short to ground inside the
motor by probing either the motor A control pin and taking the other lead to ground, or the
same can be done using motor B control pin. Motor control A is pin A and motor B control
is pin D.
If the DMM indicates and short to ground replace the transfer case actuator. If nothing
is found continue to the next step.
2. With a DMM check the resistance of the motor windings by probing pin A and pin D on the
transfer case actuator.
The DMM should indicate 0.3-40 ohms, if it does not replace the transfer case actuator
and complete the motor learn procedure. If the actuator is within specifications then
replace the transfer case control module, program, 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 Replacement
DTC C0379
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 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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