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Author Topic: 4 Wheel Drive Not Engaging  (Read 318 times)

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Neil_TX

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4 Wheel Drive Not Engaging
« on: April 24, 2018, 10:03:33 AM »

I tried to engage my 4WD into 4-Hi but all that happened was the light blinked and then it went into Auto 4WD. Every time I tried, it did the same. Anyone else had a similar issue?

I'd like to resolve myself vs. taking it somewhere to get over charged.

Avalanche Details: 2003, Z71 w/Push-Button 4WD selector
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buickwagon

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Re: 4 Wheel Drive Not Engaging
« Reply #1 on: April 25, 2018, 07:37:53 AM »

I tried to engage my 4WD into 4-Hi but all that happened was the light blinked and then it went into Auto 4WD. Every time I tried, it did the same. Anyone else had a similar issue?

I'd like to resolve myself vs. taking it somewhere to get over charged.

Avalanche Details: 2003, Z71 w/Push-Button 4WD selector

If you want to do your own diagnosis and repairs, the first step is to obtain a Factory Service Manual, they are invaluable. Second is a decent scan tool, like a Chinese Tech2 clone (search the board).

Anyway, I suspect the transfer case isn't shifting. From the FSM:

Transfer Case Shift Control Switch Indicator Flashes, then Returns to Previous Mode
Circuit Description

The transfer case shift control module controls the transfer case lock solenoid. The transfer case lock solenoid is released by being energized. This is accomplished by grounding the lock solenoid control circuit during gear shifts, and in the AUTO or adapt mode. Locking action is applied when power or ground are taken away from the lock solenoid, the transfer case motor is prevented from moving. The system is capable of providing a 2HI, 4HI and 4LO lock-up without the need of additional vehicle power to hold the transfer case in these positions.

The transfer case motor is a bi-directional, permanent magnet, D.C. motor. When energized, through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit, the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between the following ranges: 4HI, the AUTO or the Adapt mode (AWD), 2HI, Neutral (N) and 4LO.

If there is a fault in the brake control circuit, motor control A and B circuits are shorted together, or a motor control driver is damaged in the transfer case shift control module, the transfer case shift control module goes into a shift block mode. The transfer case module will also go into shift block mode if there is a mechanical concern causing the shift lever detent shaft to bind, or the transfer case shift control module is not seeing a signal from the park/neutral position (PNP) switch. The shift block mode causes the mode indicator to flash for a period of time when another mode is selected. After that period of time has ended, the indicator reverts back to the previous mode selection.
Test Description

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

2    This step determines if the battery positive or ground circuits have an open or high resistance.

3    This step helps to determine if the transfer case shift control module has the ability to command the encoder motor.

4    This step determines if motor control A and motor control B circuits being shorted together is causing a shift block.

5    This step determines if the motor control A and motor control B circuits are shorted together within the module.

6    This step determines if a binding shift lever detent shaft is causing a shift block.

7    This step has the transfer case removed and repaired.

8    This step determines if the PNP switch is sending the correct range signal.

9    This step replaces the transfer case shift control module.

10    This step determines if a short to ground, short to voltage, open, or high resistance on the transfer case lock circuit is causing a shift block.

11    This step replaced the encoder motor assembly.

stepActionyesno
1Did you perform the Diagnostic System Check - Transfer Case?Go to Step 2Go to Diagnostic System Check - Transfer Case
2Test the battery positive voltage circuit and the ground circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 11Go to Step 3
3    Turn the ignition ON, with the engine OFF.
    Install a scan tool.
    Go to ATC Data List on the scan tool and observe motor A and B current.
    Using the mode switch in the instrument panel, select the different modes.

Does the scan tool indicate an amperage draw from the motor?
Go to Step 4
Go to Step 8
4Turn the ignition OFF and disconnect the transfer case shift control module, with a DMM, check to see if motor control A and motor control B are shorted together. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 12Go to Step 5
5Connect the transfer case shift control module, with a DMM, check motor control A and motor Control B circuits for being shorted together. Refer to Circuit Testing in Wiring Systems.

Did the DMM indicate the circuits are shorted together?
Go to Step 9Go to Step 6
6Remove the encoder motor and check to see if the shift lever detent shaft is binding. Refer to Transfer Case Encoder Motor Replacement .

Is the shift lever detent shaft binding?
Go to Step 7Go to Step 10
7Remove the transfer case and repair. Refer to Transfer Case Assembly Replacement .

Did you complete the repair?
Go to Step 12-
8Check the instrument panel to see if the correct transmission range is being displayed.

Is the correct range being displayed?
Go to Step 9Go to Diagnostic System Check - Automatic Transmission In Automatic Transmission 4L60-E/4L65-E or Diagnostic System Check - Automatic Transmission In Automatic Transmission 4L80-E/4L85-E
9Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming .

Did you complete the repair?
Go to Step 12-
10Test the transfer case Lock circuit for a short to ground, short to voltage, open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 12Go to Step 11
11Replace the encoder motor. Refer to Transfer Case Encoder Motor Replacement .

Did you complete the repair?
Go to Step 12-
12    Use the scan tool in order to clear the DTCs.
    Operate the vehicle within the Conditions for allowing the symptom to occur.

Does the symptom still occur?
Go to Step 2System OK


(edited to format the chart properly)
« Last Edit: April 25, 2018, 08:01:58 AM by buickwagon »
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dna9656

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Re: 4 Wheel Drive Not Engaging
« Reply #2 on: June 21, 2018, 17:02:21 PM »

Yesterday I parked my truck in the AM leaving it in 4 X 2, went to work (8 hours) came out and I started my truck  and it was in 4 low. It took many minutes of screwing around with the buttons and after I pushed the auto 4 X 4 it clunked into 4 x 2. Ideas?
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2006 Chevy Avalanche,Z71, Upgraded to 4L65 E 2007 Standard 17" Chevy wheels but not the right year or style, new tires, exhaust, U joints, shocks, rear axle bearings and seals. New Driver's seat belt.  2007 Chrysler Sebring, 7  Yamaha motorcycles 6 Venture Royales 1 Road Star, 2 run, others for parts. 2 dachshunds, 1 house. 1 wife.

buickwagon

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Re: 4 Wheel Drive Not Engaging
« Reply #3 on: June 21, 2018, 17:54:43 PM »

Yesterday I parked my truck in the AM leaving it in 4 X 2, went to work (8 hours) came out and I started my truck  and it was in 4 low. It took many minutes of screwing around with the buttons and after I pushed the auto 4 X 4 it clunked into 4 x 2. Ideas?

Someone took it for a joy ride while you were working?

To shift into 4 low, you not only have to push the button, but the transmission must also be in neutral with the vehicle stopped or nearly so. I think that's hard to do accidentally. Given the trouble you had getting it out of 4 low,  I would suspect a possible problem with the transfer case control module, the shift motor, or the control switch(es). But that's just a guess.
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dna9656

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Re: 4 Wheel Drive Not Engaging
« Reply #4 on: June 21, 2018, 18:01:42 PM »

switches are new, thing on transfer case seems ok, I suspect the brain box. I understand HOW it's supposed to work, I'm just relating what happened/I found/experienced. I know what you have to do to change the mode of the xfer case, that's why I'm asking everybody.... WTF happened?
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2006 Chevy Avalanche,Z71, Upgraded to 4L65 E 2007 Standard 17" Chevy wheels but not the right year or style, new tires, exhaust, U joints, shocks, rear axle bearings and seals. New Driver's seat belt.  2007 Chrysler Sebring, 7  Yamaha motorcycles 6 Venture Royales 1 Road Star, 2 run, others for parts. 2 dachshunds, 1 house. 1 wife.

MS03 2500

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Re: 4 Wheel Drive Not Engaging
« Reply #5 on: June 21, 2018, 20:31:58 PM »

I'll say it can shift into 4lo by itself even while driving, in my case it was the TCCM transfer case control module was bad
 
I almost kissed the windshield.
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dna9656

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Re: 4 Wheel Drive Not Engaging
« Reply #6 on: June 21, 2018, 22:18:51 PM »

I'll say it can shift into 4lo by itself even while driving, in my case it was the TCCM transfer case control module was bad
 
I almost kissed the windshield.

So it was the thing on the tranny and not the brain in the truck?
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2006 Chevy Avalanche,Z71, Upgraded to 4L65 E 2007 Standard 17" Chevy wheels but not the right year or style, new tires, exhaust, U joints, shocks, rear axle bearings and seals. New Driver's seat belt.  2007 Chrysler Sebring, 7  Yamaha motorcycles 6 Venture Royales 1 Road Star, 2 run, others for parts. 2 dachshunds, 1 house. 1 wife.

MS03 2500

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Re: 4 Wheel Drive Not Engaging
« Reply #7 on: June 22, 2018, 10:56:25 AM »

So it was the thing on the tranny and not the brain in the truck?

I can't say for sure that is your problem, but in my case it was.

http://www.chevyavalanchefanclub.com/cafcna/index.php?topic=146881.msg2108378#msg2108378
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