Hello. I suggest further inspecting the TCCM and connector. The lights on the 4X4 switch flash when the transfer case cannot complete a shift. The incomplete shift could be caused from the encoder motor not functioning properly. The TCCM is what controls the shifting. If there is corrosion on one of the wires, that can cause a poor connection and skew the voltage or ground readings.
Disconnect the TCCM connector and check for any corrosion on the pins of the TCCM. If you see corrosion there,you will need a new TCCM. If only the wire to the TCCM is corroded,replace the corroded portion of the wire and put on a new terminal end. The terminal ends can be purchased at your local Chevy dealer.
After the repairs are made,test the 4X4 system operation. If it still has the flashing lights,follow this chart below.
Was the Transfer Case Diagnostic System Check performed?
Go to Step 2
Go to Transfer Case Diagnostic System Check
Drive the vehicle in four wheel drive mode in order to determine if torque is being applied to the front wheels (the vehicle will display crow-hop or jerking during tight turns).
Is torque being applied to the front wheels?
Go to Step 3
Go to Step 7
Does the Front Axle Switch status show the front axle Locked?
Go to Step 12
Go to Step 4
Go to Step 13
Go to Step 5
Connect a J 39200 Digital Multimeter DMM between the front axle switch harness connector terminal A and ground.
Is the voltage reading within the specified values?
Go to Step 6
Go to Step 11
Is the resistance reading within the specified values?
Go to Step 15
Does the Front Axle Actuator turn ON?
Go to Step 8
Inspect the front drive axle clutch solenoid for proper vacuum supply.
Is there proper vacuum supplied to the front drive axle clutch solenoid?
Go to Step 9
Go to Step 17
Does the front drive axle clutch solenoid engage the front axle?
Go to Step 10
Is the voltage within the values specified?
Go to Step 14
Repair an open in CKT 241. Refer to Wiring Repairs in wiring systems.
Is the repair complete?
Go to Step 19
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement.
Replace the front axle switch. Refer to front axle switch replacement.
Connect a J 39200 DMM and measure the resistance between the front drive axle clutch solenoid harness connector terminal B and the transfer case shift control module harness connector C1 terminal F4.
Is the resistance within the values specified?
Go to Step 18
Go to Step 16
Repair an open in CKT 1695. Refer to Wiring Repairs in wiring systems.
Repair an open in CKT 1570. Refer to Wiring Repairs in wiring systems.
Repair a vacuum leak between the engine and the front drive axle clutch solenoid.
Replace the front drive axle clutch solenoid. Refer to front drive axle clutch solenoid replacement.
Reconnect all ATC system components, make sure all the components are properly mounted.
Have all the ATC components been reconnected and properly mounted?
Go to Step 20
Clear all the ATC DTCs.
Are all the ATC DTCs been cleared?