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Chevrolet Silverado / GMC Sierra. Manual - part 2874
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
An open, high resistance, or short to voltage on the incremental sensor direction signal circuit will
cause this DTC to set. If the sensor is determined to be bad the entire transfer case actuator will
have to be replaced as the incremental sensor is part of the actuator and can not be replaced
independently.
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.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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 C0550
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 C0550 37
Electronic Control Unit Malfunction Watchdog/Safety Failure
DTC C0550 39
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Electronic Control Unit Malfunction Internal Electronic Failure
Diagnostic Fault Information
Circuit/System Description
This DTC indicates and RAM/ROM checksum, a EEPROM failure, or an ECU malfunction due
to an internal microprocessor failure.
Conditions for Running the DTC
The ignition is ON.
System voltage is 10.5-18 volts.
Conditions for Setting the DTC
The EEPROM, RAM and ROM, and ECM Microprocessor do self checks against one another
and the data does not match causing the DTC to set.
Action Taken When the DTC Sets
Shifting is still disabled until the DTC has cleared itself.
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
Circuit
Short to
Ground
Open/High
Resistance
Watchdog/Safety
Failure
Internal
Electronic
Failure
Electronic Control Unit
Malfunction
-
-
DTC C0550 39
DTC C0550
39
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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 sometimes possible to set this DTC falsely due to low voltage. Attempt to clear this DTC and
retest.
Circuit/System Testing
1. If this DTC sets attempt to clear the DTC and Retest.
2. If the DTC is cleared, but then resets then replace the transfer case control module,
program, and complete the transfer case 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
DTC C0569
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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