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electric 4x4 wont engage loud clunck

 
 
 
 
  #1  
Old 11-08-2006, 01:30 PM
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Default electric 4x4 wont engage loud clunck

I have a 2000 blazer that every time I push 4hi it blinks and goes back to 2hi. If I push 4low it will engage with a loud clunck. It will drive in 4low but seems to be slipping. I swapped out the switch in the cab but that did nothing. I checked the vaccum lines all are on tight and no cracks. Any clues? thanks.
 
  #2  
Old 11-08-2006, 10:13 PM
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bmxrr1990 is an unknown quantity at this point
Default RE: electric 4x4 wont engage loud clunck

i believe it is a sensor or a lil electric i wanna say oversized servo that might be the problem on my bro's 02 silverado it does the same thing except now it wont go in to anything but 2 hi
 
  #3  
Old 11-09-2006, 01:34 AM
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Default RE: electric 4x4 wont engage loud clunck

Perhaps this may help
DTC 002
Circuit Description
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.

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).



This step measures the voltage between the transfer case encoder circuit channels P, A, B, and C to ground.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



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.


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

Clear all DTCs from memory..
Operate the vehicle while pressing each of the buttons on the transfer case shift control switch.

 
  #4  
Old 11-09-2006, 08:24 AM
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tryxb is an unknown quantity at this point
Default RE: electric 4x4 wont engage loud clunck

Just purchased a 2000 Blazer and discovered the same thing but w/o the clunk. Cannot shift into 4-hi "on the fly". Can get into 4-lo if stop, put in neutral. Is it maybe same problem?
Read Chevy Lover's post but is a bit too technical for me to understand. Will this have to be corrected by Service dept. and what is approx. cost??? Thanks.
 
  #5  
Old 11-09-2006, 03:36 PM
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benz blazer is an unknown quantity at this point
Default RE: electric 4x4 wont engage loud clunck

I grounded pin 13 on the dlc and when I turned the ignition switch on all three lights blinked twice. But I dont know what code that is. Im waiting for a friend to bring him vom so I check the voltage. In my chiltons I cant find where the tranfer case encoder motor is located. Can you describe where it is. thanks
 
  #6  
Old 11-09-2006, 03:43 PM
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Default RE: electric 4x4 wont engage loud clunck

Here is a pic of where it is located...and what it looks like.

[IMG]local://upfiles/1127/997A6196AE8642B5AD153F89DA028848.gif[/IMG]
 
  #7  
Old 11-10-2006, 02:34 AM
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Chevy Lover is a jewel in the roughChevy Lover is a jewel in the roughChevy Lover is a jewel in the rough
Default RE: electric 4x4 wont engage loud clunck

20Blazer00 put up a good pic of the encoder motor, it's on the left side of the transfer case.
By grounding pin 13 and having all 3 lights flash twice, that indicates a code 2.

Next step:
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
 
  #8  
Old 11-10-2006, 08:18 PM
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Default RE: electric 4x4 wont engage loud clunck

I unpluged it and I got 4.96 volts on P,A,B and C. Does that mean its in the motor or t-case itself? Thanks for being so helpful guys.
 
  #9  
Old 11-10-2006, 08:30 PM
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Chevy Lover is a jewel in the roughChevy Lover is a jewel in the roughChevy Lover is a jewel in the rough
Default RE: electric 4x4 wont engage loud clunck

Test the encoder signal ground circuit for an open or high resistance.
If the ground signal is good, replace the encoder motor.
 
  #10  
Old 11-10-2006, 08:51 PM
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benz blazer is an unknown quantity at this point
Default RE: electric 4x4 wont engage loud clunck

Is the the female end of the plug on the t-case or is it in the male plug? Sorry if I sound dumb. I guess iam when it comes to electric stuff.
 

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