2002 2500 - Broken Transfer Case?

[Jusber15]

I have a 2001 Silverado 2500, 6.0, NP8. the service 4WD light started coming on and then the 4X4 quit as usual. I could hear the transfer case shifting but when I would try to go back to 2WD, it seemed if the tcase would stick in between gears..as if in neutral. I figured the transfer case motor was going bad and wasnt shifting it properly. I replaced the transfer case motor with a new unit and im getting the same results. I was checking if the 4WD was working down a dirt road and it wasnt. I put it back in 2WD and started driving home and got about 1/2 mile down the road and the motor revved up and wouldnt go anywhere. I messed around with the 4WD buttons and then it locked back in gear and started going again.

 

I put it back in my shop to do a bit more checking on other things. I jacked up the drivers tire and it spins freely. Lock it in 4WD and it locks in as it should. Just to be sure I pulled the front axle actuator out and verified its operation by having a helper shift it into 4WD and watching it work. I also made sure that the parts inside the actuator hole moved freely and they locked in just fine. When its locked in 4WD I can turn the front wheel with HAND FORCE. Its stiff to turn but still I dont think this should be possible if the transfer case was in 4WD.

 

What I am suspecting is that something came apart or broke in the transfer case and isnt locking things together. It does all the above even when in 4LO which definately tells me that it is shifting.

 

I had the trouble codes checked and its giving me a C0324 T-Case Lock Circuit High.

 

Anyone have any ideas on whats going on?

[bobcat5544]

DTC C0324

Circuit Description

The transfer case shift control module controls the Transfer Case Lock Solenoid. The lock is energized (locking action released, by grounding the Lock Control Circuit) during gear shifts and in AUTO 4WD mode of operation. When power or ground is removed from the lock solenoid (locking action applied, releasing the ground on the Lock Control Circuit), the Transfer Case Motor is prevented from moving. In this manner the system is capable of providing a 4H and 4L lock-up without the need of additional vehicle power to hold the Transfer Case in these positions.

 

This DTC detects a shorted lock solenoid coil, or the Lock Control Circuit shorted to 12 V.

 

Conditions for Setting the DTC

Transfer Case Lock output reads back as a high voltage when a low voltage is expected.

 

Action Taken When the DTC Sets

The system will try to turn the lock solenoid on, grounding the Lock Control Circuit; if unable to energize the solenoid, the system will not attempt to energize the solenoid again during that ignition cycle.

All shifting will be disabled.

The SERVICE 4WD indicator will be latched on for the remainder of current ignition cycle.

Conditions for Clearing the DTC

The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists.

A history DTC will clear after 100 consecutive ignition cycles without a fault present.

History DTCs can be cleared using a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

 

Measures the resistance across the encoder motor lock.

 

Tests the Transfer Case Lock circuit for a short to voltage.

 

Step

Action

Value(s)

Yes

No

 

Schematic Reference: Transfer Case Control Schematics

 

1

Was the Transfer Case Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Transfer Case

 

2

Turn the ignition OFF.

Disconnect the encoder motor.

Measure the resistance across the encoder motor lock control solenoid using a DMM.

Is the resistance reading within the specified values?

18-25 ohms

Go to Step 3

Go to Step 5

 

3

Turn the ignition OFF.

Disconnect the transfer case shift control module.

With the encoder motor still disconnected turn the ignition ON, with the engine OFF.

Probe the Transfer Case Lock circuit of the encoder motor brake control with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 6

 

4

Repair the Transfer Case Lock circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems.

 

Is the repair complete?

--

Go to Step 7

--

 

5

Replace the encoder motor. Refer to Transfer Case Motor/Encoder Replacement .

 

Is the repair complete?

--

Go to Step 7

--

 

6

Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .

 

Is the repair complete?

--

Go to Step 7

--

 

7

Use the scan tool in order to clear the DTCs.

Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK