Transfer case encoder - 2005 Chevrolet Silverado 1500HD

Question edited for clarity.

Question moved to model category.

Transfer case encoder motor alignment

Trail-voy https://www.trailvoy.com > ... > 4x4 Drivetrain

Dec 17, 2018 - Hi folks, I have been troubleshooting my 4x4 not engaging and in the process of replacing the transfer case encoder motor on my 08 ...
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Have you had it check for DTC's - diagnostic trouble codes . frustrating because you don't know what your doing. Rookies ! I'd tell you have to test but you don't have tool or knowledge .
What transfer case does your tahoe have ?
Do you know what DTC'S are ? Your vehicle 4X4 can set a bunch .

DTC B0770
DTC B0775
DTC B0780
DTC B0785
DTC B0790
DTC B2725
DTC C0300
DTC C0305
DTC C0306
DTC C0321
DTC C0326
DTC C0327
DTC C0359
DTC C0374
DTC C0378
DTC C0379
DTC C0550
DTC C0558

DTC B0775 Four Wheel Drive High Range (4HI) Indicator Circuit Malfunction

DTC B0780 Four Wheel Drive Low Range (4LO) Indicator Circuit Malfunction
DTC B0785 Two Wheel Drive High Range (2HI) Indicator Circuit Malfunction
DTC B0790 Transfer Case Neutral Indicator Circuit Malfunction

DTC B2725 ATC Mode Switch Circuit Malfunction

DTC C0300 Rear Speed Sensor Malfunction
DTC C0305 Front Speed Sensor Malfunction
Just show a few DTC'S and for everyone of these DTC'S is a diagnostic flow chart . Do you know what that is ? It's fustrating and hard to fix something when you don't have a clue as to what your doing . Do you know how to do basic automotive electrical testing ?

This would sound about what the problem could be , but with out testing id be guessing just like you .

DTC C0306 05: Motor A or B Circuit Short to Battery or Open
DTC C0306 02: Motor A or B Circuit Short to Ground
DTC C0321 01: Transfer Case Lock Short to Battery
DTC C0321 06: Transfer Case Lock Short to Ground or Open

Do yourself a favor and save some aggravation an take it to a qualified repair shop . You do know a computer controls the 4X4 system ? transfer case shift control module .

DTC C0327 Encoder Circuit Malfunction - you have a electrical circuit problem ! I suggest you take this to a ASE certified repair facility . There is a very long diagnostic process to test this !
Circuit Description
The transfer case encoder is a switch that converts a shaft position, representing a mode or range position, into electrical signals for use by the transfer case shift control module. The encoder houses 4 Hall effect sensors that are used for channels P, A, B, and C. These sensors provide a path to ground, when a magnet, (part of the Motor Encoder), passes over them.
The transfer case shift control module supplies an 8 V reference and a ground circuit for the encoder hall effect sensors to function.
The transfer case shift control module supplies current limited 5 V on all the channels, thus as these channels are pulled to ground, the module can interpret the location of the transfer case shift position.
This DTC detects an open, short to ground, or a short to voltage (12 V) in the Encoder Feed Circuit, an open in the Signal Ground Circuit, an open, short to ground, or short to voltage (12 V) in the Encoder channel circuits.

I replaced the switch assembly. Approx cost $65.00. cured my problem.

either the encoder is bad or the complete encoder motor assembly. this motor and encoder is mounted on the left side of the transfer case. easy to change.
this is the most common problem with the gm electronic transfer case.

How about to the switch , is there battery power ? Fuse #15 FWD 10amp. I/P fuse panel . BCM - body control module light's the switch indicators 2hi, 4hi,4low . Check fuse #6 10amp I/P fuse panel .
DTC 002
The transfer case encoder motor is an assembly which houses four separate channels. These channels are used to indicate to the transfer case shift control module the present gear position of the transfer case or if the transfer case is in transition between gears. The encoder motor assembly consists of an electronically conductive inner ground ring in contact with a three legged wiper arm. Each leg's length is such that it makes contact with the conductive regions of the four channels. When any leg of the wiper arm is making contact with the conductive area of any channel, the encoder provides a path to ground to the inner ground ring.
During electronic shifting, the transfer case shift control module monitors the transfer case encoder circuit for the proper operating sequence. If at any time during a shift, the encoder changes from one position to any position other than the next possible position, an error counter in the transfer case shift control module increments by four. After the counter reaches 32, the transfer case shift control module set a DTC 2, a permanent "encoder fault," and reverts to a 2HI to 4LO or a 4LO to 2HI shift pattern only. To guard against a transient, random encoder fault due to vibration, dirt, electrical noise, etc., the fault counter reduces by one each time the transfer case shift control module detects a valid encoder value. The encoder must intermittently fail 25 percent of the time for the transfer case shift control module to consider it faulty and store DTC 2.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
This step measures the voltage between the transfer case encoder circuit channels P, A, B, and C to ground.
This step tests the suspect circuit(s) for an open, short to power, or short to ground.
This step tests the encoder signal ground circuit for an open or high resistance.
DTC 2 -- Encoder Fault Step
Action
Value(s)
Yes
No
Schematic Reference: Transfer Case Control Schematics
1
Important: Check the transfer case shift control module for DTCs. The transfer case shift control module is not a class 2 device. DTCs are displayed on the transfer case shift control switch. Use the following four steps to obtain DTCs.
Turn OFF the ignition for 10 seconds.
Connect PIN 13 on the data link cable (DLC) to a ground. The DLC is located in the cab under the instrument panel on the driver's side.
Turn ON the ignition, with the engine OFF.
Observe the transfer case shift control switch select buttons for flashing codes.
Did you perform the Diagnostic System Check - Transfer Case?
--
YES - Go to Step 2
NO - Go to Diagnostic System Check
2
Disconnect the connector at the encoder motor.
Turn ON the ignition, with the engine OFF.
Measure the voltage between the transfer case encoder circuit channels P, A, B, and C to ground.
Does the voltage measure near the specified value?
4.8-5.1 V
YES - Go to Step 4
NO --Go to Step 3
3
Test the suspect circuit for an open, short to power, or short to ground. Refer to General Electrical Diagnosis and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 8
NO - Go to Step 7
4
Turn the ignition switch OFF.
Test the encoder signal ground circuit for an open or high resistance. Refer to General Electrical Diagnosis and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 8
NO - Go to Step 5
5
With a DMM at the transfer case module connector probe the encoder sign ground pin and ensure a good ground path through the module.
Did the DMM indicate a good ground path?
--
YES - Go to Step 6
NO - Go to Step 7
6
Replace the transfer case encoder motor. Refer to Motor/Encoder Replacement .
YES - Did you complete the replacement?
--
NO - Go to Step 8
--
7
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
YES - Did you complete the replacement?
--
NO - Go to Step 8
--
8
Clear all DTCs from memory. Refer to Diagnostic Trouble Code (DTC) Clearing .
Operate the vehicle while pressing each of the buttons on the transfer case shift control switch.
Does the DTC reset?
--
YES - Go to Step 2
NO - System OK

Did you ever think of having it diagnosed by a qualified repair shop ? Thier are aspects associated with this system you have no clue about. That's the first thing every one goes for , changing the switch . It flashes because codes are stored .
DTC B0768 Service Indicator Circuit High
DTC B2725 ATC Mode Switch Circuit Malfunction
DTC C0300 Rear Speed Sensor Malfunction
DTC C0305 Front Speed Sensor Malfunction
DTC C0308 Motor A/B Circuit Low
DTC C0309 Motor A/B Circuit High
DTC C0310 Motor A/B Circuit Open
DTC C0315 Motor Ground Circuit Open
DTC C0323 T-Case Lock Circuit Low
DTC C0324 T-Case Lock Circuit High
DTC C0327 Encoder Circuit Malfunction
DTC C0357 Park Switch Circuit High
DTC C0362 4LO Discrete Output Circuit High
DTC C0367 Front Axle Control Circuit High
DTC C0374 General System Malfunction
DTC C0376 Front/Rear Shaft Speed Mismatch
DTC C0387 Unable to Perform Shift
DTC C0550 ECU Malfunction
DTC C0611 VIN Information Error
You need a professional scan tool to check for these codes an too view data parameters .
Transfer Case Shift Control Module
The transfer case shift control module uses the VIN information for calculations that are required for the different calibrations used based on axle ratio, transmission, tire size, and engine. The system does not know which calibration to use without this information.
The direct battery supply line (CKT 1640) provides the power to the module and motor circuitry.
Transfer Case Encoder Motor
The transfer case encoder motor consists of a permanent magnet (PM) DC motor and gear reduction assembly. It is located on the left hand side (drivers side) of the transfer case. When activated it turns the sector shaft of the transfer case (clockwise or counter clockwise) to shift the transfer case. The encoder motor is controlled with a pulse width modulated (PWM) circuit within the transfer case shift control module. This circuit consists of a driver on both the Motor A and Motor B circuits. The encoder motor is bi-directional to allow the motor to shift the transfer case from 2HI or 4HI to neutral and 4LO positions.
Transfer Case Encoder
Your best bet ,take it to a qualified repair shop .

Checking the 4X4 control module for DTC'S - diagnostic trouble codes is what you should done . Need a factory or professional type scan tool , no an OBD2 code reader . Looking at factory service repair info. description of how it works , an testing is how to diagnose . Not guessing an throwing parts at it .
DTC B2725
The accessory switch circuit consists of 4 modes. The transfer case shift control module supplies 5 volts to the switch through the switch signal circuit. The current travels through the resistor of the currently active mode. The current on the switch signal circuit is monitored by the transfer case shift control module. The voltage on the switch signal circuit will vary depending on which mode button is pressed by the driver.
The transfer case shift control module constantly monitors the switch signal circuit to determine the condition of the accessory 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 signal circuit to determine whether the Neutral, 2HI, 4HI, or 4LO mode was selected by the driver.

DTC C0327 Encoder Circuit Malfunction
The transfer case shift control module has 4 encoder circuits, and each circuit is supplied 12 volts. These 4 circuits are A, B, C, and P, and each circuit runs to a switch located inside the encoder/motor assembly. When a particular encoder circuit is active, the switch is closed, and the 12 volts are grounded by the switch inside the encoder.
The transfer case shift control module supplies 12 volts on all the circuits. The module can interpret the location of the transfer case shift position when the circuits are grounded.
This DTC detects a fault when it compares the shift sequence/strategy to a chart located in read only memory (ROM), within the electronic control unit (ECU), within the transfer case shift control module. This is accomplished by the module reading the different combinations of encoder signals being grounded while others remain high depending on what mode or range the transfer case is in.

DTC C0550 ECU Malfunction
At each power-up, the transfer case shift control module runs a self-test on the following functions:
• EEPROM Checksum
• ROM Checksum
• RAM Checksum
• RAM Malfunction

I suggest your take your vehicle to a qualified repair shop .

Probably bad transfer case "encoder" motor. May be fuse or awd contoller also. Prior to replacing the encoder motor (try "thepartsladi" store on eBay) plug the new motor up to wiring harness at transfer case. Start car, if your light goes out bingo, yet another bad gm encoder motor! Beware aftermarket encoder motors!

How may buttons for the 4X4 two , three , or four ? Do the lights flash ? Any messages - service four wheel drive system ? Which transfer case does it have ?

Transfer Case - NVG 246-NP8 (Two Speed Automatic)
The transfer case shift control module uses the VIN information for calculations that are required for the different calibrations used based on axle ratio, transmission, tire size, and engine. The system does not know which calibration to use without this information.
Transfer Case Encoder Motor
The transfer case encoder motor consists of a permanent magnet (PM) DC motor and gear reduction assembly. It is located on the left hand side (drivers side) of the transfer case. When activated it turns the sector shaft of the transfer case (clockwise or counter clockwise) to shift the transfer case. The encoder motor is controlled with a pulse width modulated (PWM) circuit within the transfer case shift control module. This circuit consists of a driver on both the Motor Feed A and Motor Feed B circuits. The encoder motor is bi-directional to allow the motor to shift the transfer case from 2HI or 4HI to NEUTRAL and 4LO positions.
Transfer Case Encoder
The encoder is mounted to the transfer case encoder motor assembly and is replaced as an assembly. The encoder converts the sector shaft position (representing a mode or range) into electrical signals inputs to the transfer case shift control module. The module can detect what position the transfer case is in by monitoring the 4 encoder channels (P, A, B, and C). These inputs translates into AUTO 4WD, 2H, 4H, NEUTRAL, and 4L or in transition between gears.
Transfer Case Motor Lock
The transfer case motor lock is used to provide a 2H, 4H, and 4L lock-up feature. When the lock circuit is energized, the transfer case encoder motor is allowed to turn. When the transfer case is placed 2H, 4H, or 4L the motor lock circuit has no power provided to it and the lock is applied. This assures that the transfer case remains in the current gear position. When AUTO 4WD is selected the motor lock remains applied until an adaptive mode (torque is applied to the front propshaft) is required. During an adaptive mode the motor lock circuit is energized and the motor lock is released, enabling the encoder motor to turn and apply torque to the front propshaft.


SERVICE indicator (4WD/AWD) Lamp
The SERVICE indicator (4WD/AWD) lamp is an integral part of the cluster and cannot be serviced separately. This lamp is used to inform the driver of the vehicle of malfunctions within the automatic transfer case (ATC) system. The SERVICE indicator (4WD/AWD) lamp is controlled by the transfer case shift control module via a Class 2 message or by a Sevice Indicator Control Circuit.

The first thing to do before assuming it's a loose wire would be to have it checked for codes , auto zone , advance etc... can not check this codes .
DTC B0768 Service Indicator Circuit High
DTC B2725 ATC Mode Switch Circuit Malfunction
DTC C0300 Rear Speed Sensor Malfunction
DTC C0305 Front Speed Sensor Malfunction
DTC C0308 Motor A/B Circuit Low
DTC C0309 Motor A/B Circuit High
DTC C0310 Motor A/B Circuit Open
DTC C0315 Motor Ground Circuit Open
DTC C0323 T-Case Lock Circuit Low
DTC C0324 T-Case Lock Circuit High
DTC C0327 Encoder Circuit Malfunction
DTC C0357 Park Switch Circuit High
DTC C0362 4LO Discrete Output Circuit High
DTC C0367 Front Axle Control Circuit High
DTC C0374 General System Malfunction
DTC C0376 Front/Rear Shaft Speed Mismatch
DTC C0387 Unable to Perform Shift
DTC C0550 ECU Malfunction
DTC C0611 VIN Information Error

If you know nothing about this , your best bet would be to take it to a qualified repair shop .