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

On Tue, 25 Sep 2007 03:19:05 GMT, "bb" > wrote:

>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
>


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

"SnoMan" > wrote in message
...
> On Tue, 25 Sep 2007 03:19:05 GMT, "bb" > wrote:
>
> >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
> >
>
>
> 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

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

On Thu, 27 Sep 2007 15:09:43 GMT, "bb" > wrote:

>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.

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


>
>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?

You could try

>
>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.


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

On Thu, 27 Sep 2007 19:21:11 -0400, Steve Austin
> wrote:

>bb wrote:
>> "SnoMan" > wrote in message
>> ...
>>> On Tue, 25 Sep 2007 03:19:05 GMT, "bb" > wrote:
>>>
>>>> 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
>>>>
>>>
>>> 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
>>
>> 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
>>
>>
>The front axle is controlled from a switch on the transfer case.


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

"SnoMan" > wrote in message
...
> On Thu, 27 Sep 2007 19:21:11 -0400, Steve Austin
> > wrote:
>
> >bb wrote:
> >> "SnoMan" > wrote in message
> >> ...
> >>> On Tue, 25 Sep 2007 03:19:05 GMT, "bb" > wrote:
> >>>
> >>>> 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
> >>>>
> >>>
> >>> 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
> >>
> >> 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
> >>
> >>
> >The front axle is controlled from a switch on the transfer case.
>
>
> 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

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

Bobby

"bb" > wrote in message
news:kjRLi.968$6Y5.221@trnddc07...
>
> "SnoMan" > wrote in message
> ...
> > On Thu, 27 Sep 2007 19:21:11 -0400, Steve Austin
> > > wrote:
> >
> > >bb wrote:
> > >> "SnoMan" > wrote in message
> > >> ...
> > >>> On Tue, 25 Sep 2007 03:19:05 GMT, "bb" > wrote:
> > >>>
> > >>>> 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
> > >>>>
> > >>>
> > >>> 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
> > >>
> > >> 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
> > >>
> > >>
> > >The front axle is controlled from a switch on the transfer case.
> >
> >
> > 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
>
> Thanks for taking the time to type this out. I will give it a try.
>
> Bobby
>
>
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

On Mon, 01 Oct 2007 13:28:53 GMT, "bb" > wrote:

>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.


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

"SnoMan" > wrote in message
...
> On Mon, 01 Oct 2007 13:28:53 GMT, "bb" > wrote:
>
> >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.
>
>
> 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

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

On Wed, 03 Oct 2007 13:42:34 GMT, "bb" > wrote:

>
>"SnoMan" > wrote in message
.. .
>> On Mon, 01 Oct 2007 13:28:53 GMT, "bb" > wrote:
>>
>> >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.
>>
>>
>> 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
>
>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
>


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