‘04 Z71 1500 4WD issue

04cateye

New Member
Joined
Dec 31, 2024
Location
Durham
Need some 4WD diagnostic help. 4WD went away leaving me a flashing light. After reading about common problems, had the t/c motor, actuator, cabin switch replaced, and also cleaned the grounds that attach to the frame under the drivers seat.

Local technician experienced: vehicle going into 4H as expected after new parts installed, but would not come back out. Reset to N, a clunk was heard, back in 2H. 4H now flashes again when attempting to use it.

Their feeling is that something wrong inside the t/c. Another experienced Chevy fellow said it could be a million things and it is unlikely it’s the t/c. More likely the new motor is bad.

Appreciate thoughts from folks who know these trucks. It’s the Z71 5.3L gas ext. cab. Also, the TCCM will capture codes with no check engine light. Who’s a good 4WD person in Durham to diagnose rather than just throwing parts at it? Running out of money.

Thank you.
 
Last edited:
Change the fluid in it and see how that looks. That will tell you a lot about the internal health of it.

If it's empty, that's also a major problem.
 
Thanks. Got codes pulled:

Car Scanner ELM OBD2
Version: 1.112.9/1.112.9/iOS
DTC report
Connection profile: Chevrolet OBD-II / EOBDDate: 12/31/2024 12:03:51 PM
============================
OBD-II
No DTC found.
============================
ECU ID: 10
No DTC found.
============================
ECU Address $58
No DTC found.
============================
ECU Address $40ECU Address $40
DTCs: 1
----------------------------
U1000 [0xD000]
Class 2 Communication Malfunction
Status: Pending fault present, Test has not been completed
============================
ECU Address $1AECU Address $1A
DTCs: 2
----------------------------
C0379 [0x4379]
Front axle system malfunction
Status: Pending fault present, Test has not been completed
----------------------------
B0790 [0x8790]
Transfer case Neutral indicator circuit malfunction
Status: Pending fault present, Test has not been completed
============================
ECU Address $6A
No DTC found.
 
Check the connector at the encoder motor?

These are bad about water intrusion and corrosion.
 
I think you have a harness communication issue. I would find a schematic and start checking circuits.
 
Jeff B said:
I think you have a harness communication issue. I would find a schematic and start checking circuits.
Click to expand...
Thank you. What I find confusing is that I can hear the components attempting to accomplish the task when buttons are pressed. If wiring was an issue, wouldn’t the components be unpowered and unable to articulate?
 
Low voltage can wake them up but not function.

Might trace out your harness for any damage. From transfer cast and front axle to button and what ever controller that commands it.

Pinning out the harness and checking all the associated connectors using a schematic would help narrow it down.
 
This thread has some schematics related to your issue. Probably have to create an account to download though.


Schematics 2004 Silverado 1500 4.8 _ 5.3 _ 6.0 Engine_Transmission Controls

Schematics 2004 Silverado 1500 4.8 _ 5.3 _ 6.0 Engine _ Transmission Controls The schematics are .pdf format. List of Schematics Below: Automatic Transmission Inline 20-Way Connector End View (4L60E_4L65E) Automatic Transmission Inline 20-Way Connector End View (4L80E_4L85E)...
www.gearhead-efi.com
 
04cateye said:
It has a new encoder motor. Pretty sure they checked the connection.
Click to expand...
This is the type of trouble shooting logic that leads to pain.

I would t assume because the motor was changed that anyone checked the connection. Heck that might even be the source of the new problem. They didn’t get a perfect/good connection when replacing.
 
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