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Electronic transfer case not engaging

Switches flash fault code of 2. Checked voltage at encoder connector and has 8.19 volts

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Posted on Dec 16, 2016

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1998 chevy blazer four wheel drive not engageing


You replaced all those parts without knowing what is wrong , you like making parts stores rich ? Did you have it checked for DTC'S - diagnostic trouble codes ?
Transfer Case Control Module Description
The TCCM performs the following functions:
• Receives input signals
• Processes the signal information
• Develops output signals
• Sends the output signal in order to control the shifting of the transfer case
The TCCM receives input signals from the following sources:
• The transfer case shift select buttons
• The NSBU switch on the vehicles with automatic transmissions
• The clutch position switch on the vehicles with manual transmissions
• The vehicle sped sensor calibrator module
• The encoder/motor range and the mode feedback signals
• The diagnostic enable
• The front axle mechanical status signal
In order to ensure the electronic shift system is operating properly, the transfer case control module (TCCM) continually performs diagnostics checks on itself and other parts of the electronic shift system when the ignition switch is in the run position. The following are different types of system checks that the TCCM continually performs.

Motor and Relay Voltage Checks
Whenever the electric-shift motor is turned ON or OFF the motor and the electrical circuits are tested both in the de-energized and energized condition. If one or both voltage relays fail to detect the proper voltage after energizing or de-energized and energized condition. If one or both of the voltage relays fail to detect the proper voltage after energizing or de-energizing, the shift is aborted by the TCCM and a DTC of 3 is stored in order to indicate a faulty TCCM motor circuit.
If one or both relays fail to detect the proper voltage after de-energizing, both relays are turned ON by the TCCM, (even with the ignition switch positioned OFF) in order to prevent the motor from running. The TCCM then stores a DTC of 3 in order to indicate a faulty TCCM motor circuit. All of the status lamps blink three times, stop, and repeat the blinking continuously in order to alert the driver that the electronic shift system requires immediate repair. The battery will drain when this condition occurs, regardless of the ignition switch position.

DTC 001
DTC 002
DTC 003
DTC 004

DTC 001
The transfer case shift control module normally has battery voltage supplied to it at all times through the battery positive voltage circuit (CKT 40). When the ignition is ON, the transfer case shift control module conducts a self-test to determine if it retains the same memory it had when the ignition was last turned OFF. This self-test indicates whether the RAM standby power supply to the transfer case shift control module pin C6 was interrupted, which would result in clearing DTC's from memory. If the self-test fails the transfer case shift control module sets DTC 1.
Inspect the CTSY LP fuse for an open.

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.

DTC 003
Circuit Description
The transfer case encoder motor has a bi-directional, permanent magnet, D.C. motor. When energized, (through Motor Control A or Motor Control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit), the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, 2HI, and 4L ranges.
This DTC detects a short or open in the battery positive voltage circuit (CKT 1640), ground circuit, an internal short in the motor windings and related circuitry, or an internal transfer case shift control module failure.
Action Taken When the DTC Sets
In the event that one of the motor control circuits is energized (battery voltage is applied) the transfer case shift control module will energize the other motor control circuit to keep the motor from running. All switch indicator lamps will flash continuously to prompt the driver that service is required. The transfer case system will be disabled and the transfer case shift control module will remain energized even with the ignition in the OFF position.
Conditions for Clearing the DTC
The condition for setting the DTC is no longer present and a momentary loss of battery power at the battery positive voltage circuit (CKT 40).
Diagnostic Aids
When the vehicle is equipped with a manual transmission the clutch pedal must be depressed and working correctly in order for the transfer case to shift to the 4 low position. In order to confirm that it is operating correctly go the engine data 1 screen under the engine data display and observe the clutch pedal switch parameter.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
This step tests the battery positive voltage circuit (CKT 1640) for an open or high resistance.
This step inspects the ATC fuse for an open.
This step tests the ground circuit.
This step tests the Motor Control A and B circuits.
DTC 3 -- TCCM Motor Circuit Step
Action
Value(s)
Yes
No
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 A Diagnostic System Check - Transfer Case?
--
Go to Step 2
Go to Diagnostic System Check
2
Turn ON the ignition, with the engine OFF.
Backprobe and measure battery positive voltage (CKT 1640) at the transfer case shift control module.
Does the voltage measure near the specified value?
B+
Go to Step 6
Go to Step 3
3
Inspect the ATC Fuse 20A.
Is the fuse blown?
--
Go to Step 5
Go to Step 4
4
Repair the battery positive voltage circuit (CKT 1640) for an open or high resistance. Refer to General Electrical Diagnosis and Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
Go to Step 11
--
5
Repair the battery positive voltage circuit (CKT 1640) for a short to voltage or short to ground. Refer to General Electrical Diagnosis and Wiring Repairs in Wiring Systems.
Replace the ATC Fuse.
Did you complete the repair?
--
Go to Step 11
--
6
Connect a test lamp from the battery positive voltage circuit (CKT 1640) to the ground circuit at the transfer case shift control module.
Does the test lamp illuminate?
--
Go to Step 8
Go to Step 7
7
Repair the ground circuit for an open or high resistance. Refer to General Electrical Diagnosis and Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
Go to Step 11
--
8
Backprobe and measure voltage at the transfer case shift control module between the transfer case motor control A circuit and the transfer case motor control B circuit.
Press the 4HI then 4LO on the shift control switch.
The DMM should read +12V in one direction and -12V in the other direction.
Does the voltage measure near the specified value?
+12V/-12V
Go to Step 9
Go to Step 10
9
Repair the open or high resistance in the transfer case motor control A or B circuits. Refer to General Electrical Diagnosis and Wiring Repairs in Wiring Systems. If OK, replace the transfer case encoder motor. Refer to Motor/Encoder Replacement .
Did you complete the repair?
--
Go to Step 11
--
10
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Did you complete the replacement?
--
Go to Step 11
--
11
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?
--
Go to Step 2
System OK

There is a bit more to it then just replacing parts ! Your best bet - Take it to a qualified repair shop .

Feb 07, 2017 | Chevrolet Blazer Cars & Trucks

1 Answer

2003 ford f250 superduty 4x4 don't work no indicator light on dash changed4x4 switch module what next?


Check for codes. Usually part stores do it for free. here is how it works.
Principles of Operation

Electronic Shift on the Fly (ESOF) System

The electronic shift on the fly (ESOF) system is an electronic shift system that allows the operator to choose between 2 different 4x4 modes as well as 2-wheel drive. The operator can switch between 2H and 4H mode at speeds up to 88 km/h (55 mph). To engage or disengage 4L, the 4x4 generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal depressed and the transmission in NEUTRAL (or clutch pedal applied on manual transmission vehicles). This system contains pulse vacuum hublocks (PVH). The selector on the hublock, when turned fully counterclockwise to the AUTO position, engages/disengages the hub depending on the driver-selected 4x4 mode of operation. The hublocks also contain a manual override. When the selector is rotated fully clockwise to the LOCK position, the 4x4 vacuum and electronic system used for coupling the front axle to the wheel is bypassed.

The transfer case is equipped with a dual-cone synchronous clutch. This clutch is used to synchronize the front driveline to the rear. All other internals operate in the same manner as the manual shift system. When the mode select switch (MSS) on the instrument panel is turned, the 4x4 module powers the transfer case motor, which activates a shift fork and engages the clutch. When the shift motor reaches the desired position, as determined by the encoder position inputs to the 4x4 module, power to the shift motor is removed. When the transfer case front and rear output shafts are synchronized, the lockup collar mechanically engages the mainshaft hub to the drive sprocket. At this point, the front axle PVHs are engaged. Instrument cluster "4x4" and "Low Range" indicator operation is controlled via hardwired outputs from the 4x4 module.

Electronic Shift Transfer Case

The New Venture Gear NV 273 electronic shift transfer case is a 3-piece aluminium design. The unit transfers engine power from the transmission to the front and rear axles. Under normal driving conditions the unit is in 2-wheel drive high (2H), but when desired, the operator may shift into 4-wheel drive high (4H) or 4-wheel drive low (4L). The transfer case is shifted electronically. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the mainshaft.

The encoder assembly used for mode indication is of a Hall-Effect type. The system uses a total of 4 independent transistors for mode recognition. Each transistor is associated with a specific range of motor movement. When the circuit to each transistor is closed, a ground path to any of the A, B, C or D encoder pins is accomplished. When the circuit to each transistor is open, the connection to any of the A, B, C, or D encoder pins is pulled to voltage. Mode indication is "decoded" by the 4x4 module based on the varying combinations of signals coming from the transistors.

Hublock Operation

With the hublocks in the Auto position, the 4x4 ESOP system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4x4 modes. A high vacuum level (222 mm or 8.75 in. Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum level (114 to 184 mm or 5.9 to 7.1 in. Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD mode. The vacuum signals are supplied to the hublocks by system components, including the 4WD control module or GEM, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring connections, loose vacuum connections or damaged vacuum lines.

Dec 12, 2014 | 2003 Ford F250

1 Answer

Fault code co327 what to do


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.

Oct 02, 2014 | 2000 Chevrolet Silverado 2500

1 Answer

I have a 1998 Chevy Tahoe I tryed to put my truck is 4wd low and it tryed and keep on blinking and went back to 2wd and blow a fuse and I tryed again and did it again but then the the service 4wd light...


Which 4X4 system does your tahoe have ?
Transfer Case System Description (Selectable 4WD)
The New Venture Gear Model NV243 is an electronically controlled optional transfer case for use on four wheel drive K trucks. The driver selects 2HI, 4HI, or 4LO by pushing one of three illuminating shift select buttons mounted on the instrument panel. The shift select buttons display the transfer case mode and range, self-test, diagnostic trouble codes, and electronic shift mechanical engaging problems.

Transfer Case System Description (Automatic 4WD)
The two speed Auto transfer case system utilizes a part time front axle. The system allows the driver to select the transfer case position with a touch of a button. The following positions can be selected: 4-wheel drive high range (4H), All Wheel Drive (AUTO), 2 Wheel Drive high range (2H), Neutral (N), and 4-Wheel Drive low range (4L).
The Auto Transfer Case (ATC) Control Module controls all the shifting action of the transfer case based on input from the driver as well as information from the Vehicle Control Module (VCM) /Powertrain Control Module (PCM).
4WD (4H or 4L) mode: This is accomplished by engaging the front axle, applying PWM to an electric motor to apply maximum torque, (fully compressing the transfer case clutch plates) to the front axle, then removing the ground on circuit 1569, thus locking the motor in position and stop the PWM to the motor.
AUTO mode: When in this mode of operation, the system should engage the front axle, then it monitors the front and rear propshaft speeds for any speed differences. When the system senses rear wheel slip, a difference of propshaft speed between front and rear, the Auto Transfer Case (ATC) Control Module will use pulse width modulation (PWM) to drive an electric motor. This motor transfers only the required torque to the front wheels to gain additional traction on slippery surfaces up to 75 mph. There is no torque applied to the front wheels until the module senses rear wheel slip.
Throttle anticipation (only operational when in AUTO mode): If the vehicle is below 5 mph and the accelerator is pressed quickly beyond a set point, the system will automatically transfer a percentage of torque to the front wheels to help prevent the rear wheels from slipping, as in a hard acceleration from a stopped position.
The Auto Transfer Case (ATC) Control Module also has the capability of engaging the front axle while the vehicle is in motion. It does this by applying PWM to the electric motor to apply torque to the front axle, this action is used to match the speed of the front and rear propshafts. After the module senses the proper speed, it then supplies a ground on circuit 1570 to engage the front axle.
The Auto Transfer Case (ATC) Control Module will accept a mode shift only when the engine is running and a valid Motor/Encoder signal is present. A mode shift is any shift between 2H, 4H, and AUTO.
The Auto Transfer Case (ATC) Control Module will permit a range shift only if the following conditions are met within 30 seconds of the request:

Automatic 4WD Diagnostic Aids
A Scan Tool reads and displays the following information:
• Diagnostic Trouble code(s)
• Code status bit (are codes set or not)
• Transfer case lock status
• Lamp in the switch/lamp assembly
• Motor/Encoder gear position
• Ignition (3) voltage
• Front propshaft speed sensor (KPH)
• Front axle switch (open/closed)
• Front axle requested position (engaged/disengaged)
• Rear propshaft speed sensor (KPH)
• Mode switch position request
• Park switch (open/closed)
• 4WD (Adapt) Mode Auto bit
• Current Mode corrective action PWM
• Average and highest PWM applied during last slip recovery event
• Throttle anticipation mode
• Average and highest PWM applied during last Throttle anticipation corrective action event
• Difference between front and rear propshaft RPM
• Adapt event counter
• Throttle position sensor percentage

Check the transfer case shift control module for DTC's. The transfer case shift control module is not a class 2 device. DTC's are displayed on the transfer case shift control switch. Refer to Diagnostic Trouble Code (DTC) Displaying .
Are any DTC's present?
Diagnostic Trouble Code (DTC) Displaying
The transfer case shift control module is equipped with the ability to store diagnostic information, which is useful to a technician in the event of module, component or wiring failures. This information can be retrieved from the transfer case shift control module by way of flash codes, which are displayed on the three transfer case shift control switch buttons. These buttons are located on the instrument panel to the right of the steering wheel Before obtaining DTCs, perform the following transfer case control module (TCCM) Self-Test.
TCCM Self-Test
Observe the transfer case shift control switch indicators while turning the ignition switch to RUN. A properly operating system will flash all indicators and then will return to the current gear. If the system is operating normally, then proceed to Displaying Codes.
If the TCCM failed the Self-Test, then test the following circuits.
• Battery Positive Voltage (40 and 1640), and Ignition 3 Voltage for battery voltage
• Ground Circuit for ground
• Diagnostic enable circuit for an open or high resistance
• Transfer case shift control switch connector
If the above circuits are normal but the TCCM still fails the Self-Test, replace the TCCM. Refer to Transfer Case Shift Control Module Replacement .
DTC Displaying
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. Refer to Diagnostic Trouble Code (DTC) List .
Important: If the transfer case shift control switch buttons all blink only once and then stop, no fault codes are stored in the transfer case shift control module.
• When one DTC is stored in memory, that code will blink that number of times followed by a 3 second pause and then repeat.
• If more than one code is stored, the first code will blink, followed by a 3 second pause and then the second code will blink.
• This sequence will continue until PIN 13 on the DLC is no longer grounded.
• If the TCCM will not communicate the presence or absence of DTCs, test the above circuits in Self-Test Step 2. If the circuits are complete, then replace the TCCM. Refer to Transfer Case Shift Control Module Replacement .

Apr 15, 2017 | Cars & Trucks

1 Answer

I have a 1998 Chevy Blazer 4dr. The 4 whl drive switch does not light up. Some how the 4 whl drive got ingaged and now it is stuck there. I have a new switch on order but this is getting ridiculous. When...


The New Venture Gear Model NV233 is an electronically controlled optional transfer case for use on four wheel drive T trucks. The driver selects 2HI, 4HI, or 4LO by pushing one of three illuminating shift select buttons mounted on the instrument panel. The shift select buttons display the transfer case mode and range, self-test, diagnostic trouble codes, and electronic shift mechanical engaging problems.
During normal driving the transfer case is in the 2HI mode. When the transfer case is in the 2HI mode. When the transfer case is in 2HI both the 4HI and 4LO switch circuits are open, and both lights are OFF. When the four-wheel drive shift select button has been pressed, the four-wheel drive indicator lamp under the sift select button turns ON when the front axle has engaged. The shift select button will blink while the front axle is engaging. This is a normal condition.
The shifting of the transfer case is performed by a motor/encoder that receives drive signals from the transfer case control module (TCCM). When the driver selects one of the transfer case shift select buttons, request signals are sent to the TCCM. If the correct input signals exists, the TCCM will send drive voltages to the motor/encoder. The motor/encoder will position the transfer case to the ordered shift position.

Transfer Case Control Module Description
The TCCM performs the following functions:
• Receives input signals
• Processes the signal information
• Develops output signals
• Sends the output signal in order to control the shifting of the transfer case
The TCCM receives input signals from the following sources:
• The transfer case shift select buttons
• The NSBU switch on the vehicles with automatic transmissions
• The clutch position switch on the vehicles with manual transmissions
• The vehicle sped sensor calibrator module
• The encoder/motor range and the mode feedback signals
• The diagnostic enable
• The front axle mechanical status signal
In order to ensure the electronic shift system is operating properly, the transfer case control module (TCCM) continually performs diagnostics checks on itself and other parts of the electronic shift system when the ignition switch is in the run position. The following are different types of system checks that the TCCM continually performs.
Data Memory Retention Check
The TCCM checks the stored diagnostic trouble code memory to see if the memory has changed since the ignition switch was last positioned to OFF. This self test checks in order to see if the RAM standby power supply has been interrupted. If the TCCM detects a RAM standby power supply interruption, (the loss of stored diagnostic trouble code) the TCCM stores a DTC of 1 indicating RAM standby power failure.
This condition occurs when the TCCM is disconnected from the wiring harness or battery power is removed. The DTC of 1 automatically clears from the TCCM after cycling the ignition switch ON and OFF five times.

Before replacing parts you should test the system !
Diagnostic Trouble Code (DTC) Displaying
The transfer case shift control module is equipped with the ability to store diagnostic information, which is useful to a technician in the event of module, component or wiring failures. This information can be retrieved from the transfer case shift control module by way of flash codes, which are displayed on the three transfer case shift control switch buttons. These buttons are located on the instrument panel to the right of the steering wheel Before obtaining DTCs, perform the following transfer case control module (TCCM) Self-Test.
TCCM Self-Test
Observe the transfer case shift control switch indicators while turning the ignition switch to RUN. A properly operating system will flash all indicators and then will return to the current gear. If the system is operating normally, then proceed to Displaying Codes.
If the TCCM failed the Self-Test, then test the following circuits.
• Battery Positive Voltage (40 and 1640), and Ignition 3 Voltage for battery voltage
• Ground Circuit for ground
• Diagnostic enable circuit for an open or high resistance
• Transfer case shift control switch connector
If the above circuits are normal but the TCCM still fails the Self-Test, replace the TCCM. Refer to Transfer Case Shift Control Module Replacement .
DTC Displaying
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. Refer to Diagnostic Trouble Code (DTC) List .
Important: If the transfer case shift control switch buttons all blink only once and then stop, no fault codes are stored in the transfer case shift control module.
• When one DTC is stored in memory, that code will blink that number of times followed by a 3 second pause and then repeat.
• If more than one code is stored, the first code will blink, followed by a 3 second pause and then the second code will blink.
• This sequence will continue until PIN 13 on the DLC is no longer grounded.
• If the TCCM will not communicate the presence or absence of DTCs, test the above circuits in Self-Test Step 2. If the circuits are complete, then replace the TCCM. Refer to Transfer Case Shift Control Module Replacement .

Is the 4WD fuse # 15 -10 amp located in the I/P fuse box good ?

Jul 30, 2017 | 1998 Chevrolet Blazer

1 Answer

I have a 97 Chevy blazer with push button 4 wheel drive and it don't shift In to 4 low or 4 hi and the light should flash for 30 second then go back to 2 hi if it can't shift but when you push the button...


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

Aug 29, 2017 | 1997 Chevrolet Blazer

3 Answers

My 2000 gmc jimmy 4x4 stoped working. It wont go into 4 hi. the vacume pump under the battery is good. can hear and feel the motor switch from 4 low to 2 hi. any ideas? Is there a code reader for this...


Hi, it sounds like your front diff engages but your transfer case is not. raise one of your front tires off the ground and see if it will lock up when you go to 4hi. If it does then the problem is your encoder motor that hangs down under your transfer case.

Aug 21, 2010 | 2000 GMC Jimmy

1 Answer

Canyon 4wheeldrive light turned on


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 .

Dec 31, 2017 | 2005 GMC Canyon

1 Answer

2004 silverado 4 wheel drive does not work, 4 wheel high button remains lit, will not change to any other button


1. Inspect Transfer Case Control Module (TCCM) and encoder/motor wiring, terminal contact, grounds.

2. Install updated TCCM calibration.

3. Inspect for TCCM water intrusion.
4. Replace transfer case encoder/motor. 1. Check voltage on pin A, Light Blue wire at the engage switch.

2. The voltage should remain near 1.0v with no buttons pushed, compare to the value on the scanner when the problem happens.

3. Back close to the switch by hand and check for a glitch.

4. Wiggle tug test harnesses at the switch and TCCM.

5. Check terminal to pin grip. could be your transfercase control module locater under drivers side of dash. or the encoder motor

Oct 23, 2009 | 2004 Chevrolet Silverado 1500 Crew Cab

1 Answer

4wd 1999 chevy 2500 will not engage


1999 chevy 2500 ??? Come on a warranty , get real . Did you have the 4X4 system checked for DTC'S - diagnostic trouble code's ? Can set a few .
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 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

The range/mode switch circuit consists of four normally open switches. The automatic transfer case control module supplies a regulated 8 volt DC to the switch through circuit 431. The switch has circuit 1693 to return current to the automatic transfer case control module through a 9.09K ohms resistor located inside the switch.
The transfer case shift control module constantly monitors this signal voltage to determine the condition of the mode switch circuit. If no buttons are pressed, and the transfer case shift control module detects a voltage level outside the possible range (approx.-0.5 to 1.0 volts) for longer than 5 minutes, the transfer case shift control module will set this DTC or if a button is held down or sticks for a period longer than 5 minutes.
When each of the switches is depressed they will complete a circuit through their own specific resistor. The transfer case shift control module continuously monitors the switch input to determine whether the 4HI, AUTO 4WD, 2HI, and 4LO button selections are made by the driver. Neutral may be obtained if the following conditions are met:
• The engine is running.
• The automatic transmission is in neutral (or the clutch pedal is depressed on a manual transmission application).
• The vehicle speed is below 3 MPH.
• The transfer case is in the 2HI mode.
Once these conditions have been met, pressing and holding both the 2HI and 4LO buttons for 10 seconds will shift the transfer case into neutral, turning on the red neutral indicator lamp.
If you are not familiar with these electronic systems ,I suggest you take your vehicle to a qualified repair center .

Nov 09, 2017 | 1985 Chevrolet S-10 Blazer

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