4wd will not lock in - 1996 Chevy Pickup

I have a 1996 Chevy K1500 Pickup with the pushbutton 4 wheel drive. The front will not lock in and the light on the dash just blinks. I pulled the actuator and connected to battery and it extends. I checked voltage on
connector and had 12v but when I plug the actuator in, the voltage drops to 0 and the actuator does not extend. I checked voltage at the fuse and it stays at 12v. I reinstalled the actuator and connected to battery so the plunger should extend and the dash light turns solid on. I feel this points at a bad connector or a failing relay but none of the relays in the fuse box are called 4wd or anything similar.
Where do I look for the bad connection or bad relay? I will dig into dash tomorrow but don't have a wiring diagram.
Thanks for any help. Bobby
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It could be a bad servo ECM/controller. The servo could be drawing too much power for it or it is bad. Based on what you did I would check it first. Reason like this is why I would never own a "Push n Pray" 4x4 drive system. ----------------- TheSnoMan.com
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wrote:

the
to
the
dash
I assume teh ECM/Controller is the engine control computer. How do I check that? Also, I tried to trace the wires from the actuator but they go into a bundle and not very easy to trace. Do they go to the ECM next or do the go to the dash buttons? Where is the control of the current coming from? I disconnected and reconnected the dash buttons with no difference hoping a connection was bad. I'm hoping the wires from the actuator connect directly to the buttons on the dash and that little box controls the front axle.
Before I do much to test the ECM (since I will not replace it if this is all that is wrong), I will run a new pair of wires to the actuator on a seperate switch. Any problem with this?
Kinda funny but I ordered the truck in 1996 with the lever on the floor. It came with the push buttons. Almost didn't take it but I think the lever system has this same locking actuator for the front axle.
Thanks again for all comments. Bobby
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It has a seperate contoller called TCCM or TCSCM. It is located under dash behind lower dash panel. This controls output to encoder motor on Tcase and front actuator

You could try

Yes manual shift has same actuator on front axle but that model year truck had a thermo actuator that were trouble some. GM switched over to a servo driven one around 1998 (98's had them but not sure about 97's) There is retro kit to allow you to use newer style on a truck that year. ----------------- TheSnoMan.com
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bb wrote:

The front axle is controlled from a switch on the transfer case.
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On Thu, 27 Sep 2007 19:21:11 -0400, Steve Austin

Try this
The diagnostic trouble codes are displayed on the three transfer case shift select buttons. The shift select buttons are located on the instrument panel when the connector pin 13 on the data link cable is grounded, and the ignition switch has been OFF for at least five seconds prior to positioning the ignition switch to run the shift select buttons will blink various times together in order to indicate a diagnostic trouble code from 1 to 4. Position the ignition switch to OFF. Ensure the ignition switch is positioned to OFF for at least 6 seconds. Connect pin 13 on the data link cable to a vehicle ground source. The data link connector is located in the cab under the instrument panel on the drivers side. Position the ignition switch to RUN. Note the shift select buttons for blinking codes. Refer to Diagnostic Trouble Codes . If the shift select buttons all blink one time and stop, and do not continue to blink, no fault codes are stored in the TCCM. The transfer case shift select buttons will blink in order to identify any stored DTC. If only one code is stored in the TCCM memory, that code will blink repeatedly with a three second delay between blinking sequences. If more than one code is stored, the first code will blink once, then after a three seconds delay, the next code will blink. This sequence will continue until pin 13 is no longer grounded. When reading the diagnostic trouble codes, the number of shift select buttons blinks will indicate the code number. ----------------- TheSnoMan.com
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wrote:

The
pulled
on
drops
and it

the
this
in
check
into a

the go

I
a
directly
is all

seperate
floor. It

lever
Thanks for taking the time to type this out. I will give it a try.
Bobby
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wrote:

voltage
so
into
too
it
from?
hoping
axle.
I grounded pin 13 and lights flash once and go out. I looked for the TCCM to reseat the connector but not sure what it looks like. I found a unit under the dash that is on a little bracket that just rests in a grove. It is located just to the right of the driver, above the gas peddle and just to the left of the AC duct. I could not see how to get that thing out though and remove the connector. If that is it, any advice on how to remove and what could be the problem would be appreciated.
Thanks again, Bobby
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You have found the TCCM module. As far as removing it, manual says there is 2 screws holding it in and thaey have to be removed to lower unit to gain access to connector on it. (screws remvove from driver side and at bottom of bracket)
----------------- TheSnoMan.com
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wrote:

TCCM
It
to
though
SnoMan, Thanks for all of the help but one more question. If there are no codes, is the connector the likely problem? Do the wires from the TCCM go directly to the actuator or is there a relay somewhere in the path. The TCCM doesn't come out very easily.
Thanks, Bobby
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There is a switch on Tcase that activates a relay that engages front axle. Tcase engages first because it has a syncronizer to bring fron axle shaft up to speed first so that actuator can then be engaged. ----------------- TheSnoMan.com
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SnoMan wrote:

No relay. Just a switch on the t-case. The brown wire is power. The light blue wire runs to the front axle actuator. The grey and black wire is a signal to the pcm.
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wrote:

unit
grove.
just
and
are no

go
The
I've been out of town a couple of days so just getting back to this. Thanks so much for the details. I will look for this switch and most likely replace it.
Thanks, Bobby
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wrote:

unit
grove.
just
and
are no

go
The
I finally got back to looking at the truck again and did some surfing. I called the Chevy house and the guy there said he didn't see just a switch listed. Do I have to change the assembly or is the switch servicable (clean contacts)?
thanks again, Bobby
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