4 wheel selection not working properly?

Hello,

9 times out of 10 it will be the encoder motor on the transfer case. Here is the location and how to change it out in the diagrams below. Check out the diagrams (below). Please let us know what happens.

I would start by checking to see if the front axle actuator under the truck on the passenger side of the differential is connected (item 8). It's possible it wasn't connected fully or that it has a bad connection. Either one would keep the front axle from locking in and give you no 4X4.

So we need to find out when you shift to 4WD if the front drive shaft is spinning? As you will see from the attachments on how this works that the switch just send signal to the actuator to engage the axles but if the transfer case is not spinning the front drive shaft to spin the front axle. If this is not happening then the issue is in the shifter or the transfer case itself. If the front drive shaft is spinning then we need to look into wiring issues to the switch or actuator. Does the 4WD indicator come on like it should?

If you can hear the transfer case shifting, then chances are there is a vacuum leak to the front axle. Check for leaks or damaged vacuum hoses from the engine to the transfer case and then the front axle. If they are all good, make sure you are getting power to the 4wd actuator and it is working properly.

Let me know if you have other questions.

Joe

Have you checked for vacuum leaks at the front axle? When you say actuator, are you referring to the one on the transfer case or the front axle?

Is there power to the actuator on the front axle? I'm trying to remember if the axle actuator is vacuum or electric actuated. So much has changed in 6 (sorry, 7) years. If the transfer case is working, then either the actuator on the axle isn't or you have an internal problem within the axle. You may need to start taking things apart.

If the service 4wd light was on, you need to have the computer scanned to identify where the problem is coming from. Most parts stores will do it for free.

Let me know what you find.

Joe

Modern vehicles can be sensitive to electrical issues. An extreme inrush of exterior power(as in a "jump start")can sometimes cause unexpected problems. Large voltage excursions can damage sensitive modules and render some functions inoperative. I suggest your schedule an appointment with your Chevrolet service provider straightaway.

As far as the transfer case is concerned, when the neutral condition occurs, does the indicator show neutral? To electronically shift into neutral requires simultaneously pressing 2hi and 4lo. This specific resistance value(or volt drop) is interpreted by the module, and corresponds to the selected range output. Is this what the transfer case and module were replaced in attempt to correct? What do the switch indicators do when this happens? I am not certain what would happen, but if you are selected in 2hi, and you disconnect the encoder on the case, would it stay in 2hi. If that is the case, it may be worth a try to see if the problem is still reproduced. If so, I would say you have something going on in the case(mechanical). You may have some corresponding service 4WD indicator, and some codes set, but you should still be able to operate it, and the codes would clear when normal operation is resumed. Otherwise, you may need a scan tool that would communicate with the ATC module, and check to see if inputs are telling it to go into neutral.
As far as the wipers are concerned, I don't see how they would be related to the transfer case. So you have high speed, lo speed respectively, but no intermittent? When the switch is in intermittent, do the wipers just stop anywhere on the windshield, or do they continue on lo speed with no pulse? My first guess would be a wiper module that has the switch signal shorted to voltage internally, It could also be a switch. I will forward you the diagnostic chart for wipers always on.

Wipers Always On
Step
Action
Yes
No

Schematic Reference: Wiper/Washer Schematics

Connector End View Reference: Wiper/Washer Connector End Views Lighting Systems Connector End Views

DEFINITION: Windshield wipers are always ON at low or high speed.

1
Did you review the Wiper/Washer System Description and Operation and perform the necessary inspections?
Go to Step 2
Go to Symptoms - Wiper/Washer Systems

2
Turn the windshield wiper/washer switch OFF.
Turn the ignition ON, with the engine OFF.
Are the windshield wipers always on?
Go to Step 3
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3
Turn the ignition OFF.
Disconnect the turn signal multifunction switch connector C3.
Turn the ignition ON, with the engine OFF.
Are the windshield wipers always on?
Go to Step 4
Go to Step 7

4
Are the windshield wipers always ON at high speed?
Go to Step 5
Go to Step 6

5
Test the windshield wiper switch high signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 11
Go to Step 9

6
Test the windshield wiper switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 11
Go to Step 9

7
Inspect for poor connections at the windshield wiper/washer switch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 11
Go to Step 8

8
Replace the windshield wiper/washer switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?
Go to Step 11
--

9
Inspect for poor connections at the windshield wiper motor module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 11
Go to Step 10

10
Replace the windshield wiper motor module. Refer to Windshield Wiper Motor Replacement.

Did you complete the replacement?
Go to Step 11
--

11
Operate the system in order to verify the repair.

Did you correct the condition?
System OK
Go to Step 3

Good morning,

I attached a wiring diagram of the system for you to view.

Check the fuses I circled to be sure they have power on both sides with the key on.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

You need to test for voltage to the motor on the transfer case to be sure the motor has the power to change to 4 wheel.

https://www.2carpros.com/articles/how-to-check-wiring

Roy

Transfer Case Motor/Encoder Replacement

Removal Procedure

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1. Raise and suitably support the vehicle. Refer to Vehicle Lifting.
2. Remove the transfer case shield.
3. Remove the front propeller shaft.
4. Remove the motor/encoder electrical connectors.

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5. Remove the motor encoder mounting bolts.
6. Remove the motor encoder assembly.
7. Remove the motor encoder gasket.