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Jettadan1, Chevy Technician
Category: Chevy
Satisfied Customers: 5064
Experience:  Most of our fleet is chevy.
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2004 1500 Z71 Silverado with auto 4WD..Transfer Case Control Module

Customer Question

Have a 2004 1500 Z71 Silverado with auto 4WD getting a CO327 error code. Having trouble figuring out if it's the Transfer Case Control Module or if it could be one of the hall censors? Any trouble shooting tips?
Submitted: 6 years ago.
Category: Chevy
Expert:  Jettadan1 replied 6 years ago.

Hello, I am Daniel. I may ask you questions, to better answer you. Please let me know if you have any other questions before you Accept.



The transfer case encoder is an analog sensor that returns a signal that represents the physical position of the transfer case sector shaft. This signal represents the mode or position that the transfer case is currently in. This sensor is made up of the following 3 circuits:

  • A 5-volt reference circuit.
  • An encoder signal circuit.
  • An encoder low reference circuit.

This DTC detects an out of range reading from the encoder signal, a short to voltage on the 5-volt reference circuit.


You can not test the encoder signal with out a scan tool to see if its out o f range.


You will want to check wires to trans case and transfer case connections and to encoder sensor. Its common that the encoder sensor is bad but could betrans case shift control module. This if wires and connections are good but with out a scanner to do most of the testing it will be hard. You will want to get one.

Customer: replied 6 years ago.
I have a mechanic that has a Snap On scanner who will work with me. What trouble shooting can we do with the scanner to better diagnose the problem?
Expert:  Jettadan1 replied 6 years ago.
Once you get the code you should have a trouble shooting menu to take you through the flow of diagnosis. first you will want to view the different voltage parameters, then view the encoder voltage then with emergency brake on and in nuetral scan the encoder parameters on voltage in the transfer case data list. select each of the positions and make sure the value stays whithin 0.5 to 4.5 volts
Expert:  Jettadan1 replied 6 years ago.
Let me know when your ready for next step. I will be on til 100 in the after noon tomarrow from about 930. its 519 my time now. We can work on it when you get the scanner if you wish.
Customer: replied 6 years ago.

Sounds good. Thank you. How do I find you tomorrow & will I have to pay you again or how does this work?