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Chevrolet Silverado / GMC Sierra. Manual - part 2869
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 4 low indicator off and on. If the 4 low indicator is still inoperative
short to 4 low indicator control to ground, if the 4 low indicator lights replace the module,
program, and complete the motor learn procedure. If the 4 low indicator is still inoperative
replace the switch.
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 B0785
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 B0785 01
2 High Indicator Circuit Short to Battery
DTC B0785 06
2 High Indicator Circuit Short to Ground or Open
Diagnostic Fault Information
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
2 High Indicator Circuit
DTC B0785 DTC B0785 DTC B0785
-
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Circuit/System Description
The 2 high indicator circuit consists of an interior lights dimming circuit and an 2 high indicator
control circuit. When the 2 high mode has been selected, current is supplied to the 2 high
indicator by the interior lights dimming circuit, traveling through the 2 high indicator LED, at
which time the transfer case shift control module supplies the ground through the 2 high indicator
lamp control circuit.
Conditions for Running the DTC
The ignition is ON.
System voltage is 10-18 volts.
Conditions for Setting the DTC
The system monitors the voltage on the 2 high indicator control circuit.
If the system detects a voltage of 2 volts or less for 1.5 seconds when the 2 high indicator is
not commanded, the DTC is logged.
If the system detects a voltage of 4.5 volts or more when the 2 high indicator is commanded,
the DTC is logged.
Action Taken When the DTC Sets
The SERVICE 4WD indicator is not commanded on for this DTC.
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
06
06
01
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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 2 high indicator control circuit will cause the 2 high indicator to remain
on at all times. An open or high resistance will cause the 2 high indicator to be inoperative during
the 2 second bulb check.
Circuit/System Testing
Check the interior dimming circuit pin 2 at the transfer case shift control switch for voltage for
the 2 seconds after turning the ignition on during the bulb check.
If less than battery voltage check the interior lights dimming circuit for an open or high
resistance. If the voltage is low or non existent and the circuit tests good replace the BCM.
If the interior dimming circuit and BCM test good go to the next step.
If the 2 high indicator is on at all times check the 2 high indicator control circuit for a short
to ground. If the 2 high indicator is inoperative during bulb check, check the 2 high
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 2 high indicator off and on. If the 2 high indicator is still
inoperative short to 2 high indicator control to ground, if the 2 high indicator lights replace
the module, program, and complete the motor learn procedure. If the 2 high indicator is still
inoperative replace the switch.
Repair Procedures
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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 B0790
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 B0790 01
Neutral Indicator Circuit Short to Battery
DTC B0790 06
Neutral Indicator Circuit Short to Ground or Open
Diagnostic Fault Information
Circuit/System Description
The neutral indicator circuit consists of a 12 volt reference circuit and a neutral indicator control
circuit. When the neutral mode has been selected, current is supplied to the neutral indicator by
the 12 volt reference circuit, traveling through the neutral indicator LED, at which time the
transfer case shift control module supplies the ground through the neutral indicator control
circuit.
Conditions for Running the DTC
Circuit
Short to
Ground
Open/High
Resistance
Short to
Voltage
Signal
Performance
Neutral Indicator Circuit
DTC B0790
06
DTC B0790
06
DTC B0790
01
-
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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