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Chevrolet Silverado / GMC Sierra. Manual - part 2914
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 neutral indicator control circuit will cause the neutral indicator to
remain on at all times. An open or high resistance will cause the neutral indicator to be
inoperative during the 2 second bulb check.
Circuit/System Testing
Check the ignition 12 voltage reference circuit pin 2 at the transfer case shift control switch for
voltage with the ignition on.
If less than battery voltage check the 12 volt reference circuit pin 14 at the BCM and pin 2
on the transfer case mode switch for an open or high resistance. If the voltage is low or non
existent and the circuit tests good replace the BCM. If the BCM test good go to the next
step.
If the neutral indicator is on at all times check the neutral indicator control circuit for a
short to ground. If the neutral indicator is inoperative during bulb check, check the neutral
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 neutral indicator off and on. If the neutral indicator is still
inoperative short to neutral indicator control to ground, if the neutral indicator lights
replace the module, program, and complete the motor learn procedure. If the neutral
indicator is still inoperative replace the switch.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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 B2725
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 B2725 08
Active Transfer Case Mode Switch Circuit
Diagnostic Fault Information
Circuit/System Description
The active transfer case mode switch circuit consists of 5 modes. The transfer case shift control
module supplies 5 volts to the switch through the 5-volt reference circuit. The current travel
through the resistor of the currently active mode. The current is then returned to the transfer case
shift control module through the switch signal circuit. The transfer case shift control module
constantly monitors this signal voltage to determine the condition of the mode switch circuit.
When each of the modes are selected they complete a circuit through their own specific resistor.
The transfer case shift control module continuously monitors the switch input to determine
whether the Neutral, AWD, 2HI, 4HI, or 4LO mode was selected by the driver.
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Invalid
Active Transfer Case Mode
Switch Circuit
DTC B2725
08
DTC B2725
08
DTC B2725
08
DTC B2725
08
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Conditions for Running the DTC
The ignition is ON.
System voltage is 10.5-18 volts.
Conditions for Setting the DTC
The system constantly monitors the voltage on switch signal circuit.
If the system detects a voltage level under 0.38 volts or greater than 4.86 volts for 60
seconds, the DTC is logged.
Action Taken When the DTC Sets
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
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Scan Tool Reference
Scan Tool Data List
Scan Tool Data Definitions
Diagnostic Aids
A short to ground on the neutral indicator control circuit will cause the neutral indicator to
remain on at all times. An open or high resistance will cause the neutral indicator to be
inoperative during the 2 second bulb check.
Circuit/System Testing
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.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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