Service 4 wheel drive ...message

[2-H2's]

I've had my truck in for mods lately & went to pick it up today. The message wasn't there a month ago when I took it in? The vehicle is an '05 SUT, just installed the FabTech lift, two Gobi's, 6 Pia's, dual battery setup, along with new tires & wheels.

I took the truck to the stealership earlier today;

First comment was, "this truck has been recently modified"...No shiat!!!

Second comment was, "no warranty"

My response was; "get Hummer on the telephone, so we can settle this, NOW!!!"

They backed off slightly & decided to look at it. Their first diagnosis was a faulty encoder motor. They replaced it & the message was still present. So now I have an appointment on Monday to bring it back in...Until then…

I pose my question for the gods, messiahs & hummer techs on this forum. Any ideas as to what might be causing this message???


LC

[H2Finally]

Originally posted by PhilD:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by 2-H2's:
Any ideas as to what might be causing this message???

Yes, there is something wrong with the 4WD system

It should be warranty item, unless they can say with some certainty that your mods may have caused the problem. Which they obviously can't because they don't know what it is yet.

I presume that the lift installers checked to make sure they had not disconnected anything?

The t-case controls the Service 4WD light I believe. Assuming they are using a scan tool and it shows no DTC's for the t-case, then they should command the service light to go off and if it goes off, then replace the transfer case shift control module. If the service light does not go off, they should check the instrument cluster for faults. Once they have replaced the module, they should see if they can get the serive light to come back on, try all modes, etc. </div></BLOCKQUOTE>Phil, isn't this one of those instance whereby if the dealer did all those work, and finally tracked the problem down, and it turns out the problem was caused by the guys did the lift install -- then 2-H2's would be responsible for all costs dealer has incurred?

[PARAGON]

Well, I would try to look it up to see what they could glean from the Tech2 but I've got to reinstall my Si software once again. tomorrow

[MarineHawk]

Doubt you have the same problem, but my Sierra had the same basic DIC message appear, and it would not transfer out of 2WD-Hi to either of the 4WD settings. I disconnected my battery for a couple of minutes and reconnected it. It worked fine and never happened again.

[2-H2's]

Now that I have calmed down...

I seriously doubt the installers did anything other than lift the truck. They may or may not have bumped into or disconnected something which caused this message.

However, after further review this morning I tried to engage the four wheel drive elements and no workie... That alone makes me assume that something internally or computer controlled is malfunctioning. I seriously doubt it had anything to do with the mods.

MH I have already disconnected the battery during the dual setup & again last night.

PhilD Thanks for the vote of confidence...

H2Finally I understand your logic...but a truck with 3.5K miles on it???

I certainly hope Hummer can solve the problem & resolve the issue. So far only Hummer has taken the "it ain't our problem approach". That's just shiatty in my book to immediately void a warranty. I just want it fixed, then we can remedy the who's fault it is.

Side note*** The installer doesn't have a problem repairing or paying for any of his faults. He had already taken it to another GM dealer prior to my arrival & they couldn't figure out what was causing the message. He is the one who wanted it taken to an authorized "hummer" dealer to figure this all out.

All I can do now is what until Monday...


LC

[PARAGON]

<H1>DTC C0306</H1><A name=ss1-841813><A href="#ss1-841813">
<H5>Circuit Description</A></H5>


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: </P>
<UL type=BULLET>
<LI>4HI
<LI>4HI Lock
<LI>4LO Lock
<LI>N </LI>[/list]

This DTC detects an open, short to voltage, or short to ground in the motor
control A or motor control B circuits, or an open, or short to ground inside the
motor.</P><A name=ss2-841813><A href="#ss2-841813">
<H5>Conditions for Running the DTC</A></H5>
<UL type=BULLET>
<LI>The ignition is ON.
<LI>System voltage is 9-18volts. </LI>[/list]<A name=ss3-841813><A
href="#ss3-841813">
<H5>Conditions for Setting the DTC</A></H5>
<UL type=BULLET>
<LI>The system will test the motor circuits by checking for unwanted voltage.
<LI>Then, the system supplies voltage on each of the motor circuits and reads
the voltage back on the other circuit.
<LI>If the system detects a problem with the circuits, the DTC is logged. The
transfer case shift control module senses a low voltage return in the motor
control A or motor control B circuits when a high voltage is expected.
<LI>The fault must remain current for 1.2seconds to set the DTC.
</LI>[/list]<A name=ss4-841813><A href="#ss4-841813">
<H5>Action Taken When the DTC Sets</A></H5>
<UL type=BULLET>
<LI>All shifting will be disabled.
<LI>The SERVICE 4WD indicator will remain illuminated for the remainder of the
current ignition cycle. </LI>[/list]<A name=ss5-841813><A href="#ss5-841813">
<H5>Conditions for Clearing the DTC</A></H5>
<UL type=BULLET>
<LI>The transfer case shift control module will clear the DTC if the condition
for setting the DTC is not currently present.
<LI>A history DTC will clear after 100 consecutive ignition cycles without a
fault present.
<LI>History DTCs can be cleared using a scan tool. </LI>[/list]<A
name=ss6-841813><A href="#ss6-841813">
<H5>Test Description</A></H5>


The numbers below refer to the step numbers on the diagnostic table.</P>

1. <A name=TD02>
   <LI value=2>
   
   
   Tests motorA driver high for proper operation.</P><A name=TD03>
   <LI value=3>
   
   
   Tests motorB driver high for proper operation.</P><A name=TD04>
   <LI value=4>
   
   
   Tests motorA driver low for proper operation.</P><A name=TD05>
   <LI value=5>
   
   
   Tests motorB driver low for proper operation.</P><A name=TD06>
   <LI value=6>
   
   
   Tests motor controlA and motor controlB circuits for being
   shorted together.</P><A name=TD07>
   <LI value=7>
   
   
   Tests motor controlA for a short to ground, short to voltage, open, or
   high resistance.</P><A name=TD08>
   <LI value=8>
   
   
   Tests motor controlB for a short to ground, short to voltage, open, or
   high resistance.</P></LI>

<TABLE width="100%" border=1>
<TBODY>
<TR>
<TH vAlign=bottom align=middle>


Step</P></TH>
<TH vAlign=bottom align=middle>


Action</P></TH>
<TH vAlign=bottom align=middle>


Value(s)</P></TH>
<TH vAlign=bottom align=middle>


Yes</P></TH>
<TH vAlign=bottom align=middle>


No</P></TH></TR>
<TR>
<TD vAlign=bottom colSpan=5>


Schematic Reference: <A
href="/servlets/CellHandler?CellId=69955&RefDoc=841813&evc=sm">Tra nsfer
Case Control Schematics</A> </P>


Connector End View Reference: <A
href="/servlets/CellHandler?CellId=69957&RefDoc=841813&evc=sm">Tra nsfer
Case Control Connector End Views</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S01>


1</P></A></TD>
<TD vAlign=top align=left>


Did you perform the Diagnostic System Check - Transfer Case?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step2 </P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=69959&RefDoc=841813&evc=sm">Dia gnostic
System Check - Transfer Case</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S02>


2 </P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Engage the parking brake.
   <LI type=1>Turn the ignition OFF and raise the vehicle on a hoist.
   <LI type=1>Disconnect the motor encoder connector at the transfer case.
   <LI type=1>Turn the ignition ON.
   <LI type=1>With a DMM, measure voltage by probing the motor controlA
   circuit and take the other lead to a good ground.
   <LI type=1>With a scan tool, command motorA driver high ON. </LI>

Does the DMM indicate battery voltage?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step3 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step7 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S03>


3</P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>With a DMM, measure voltage by probing the motor controlB
   circuit and take the other lead to a good ground.
   <LI type=1>With a scan tool, command motorB driver high ON. </LI>

Does the DMM indicate battery voltage?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step4 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step8 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S04>


4 </P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>With a DMM, measure voltage by probing the motor controlA
   circuit and take the other lead to ground.
   <LI type=1>With a scan tool, command motorA driver low ON. </LI>

Does the voltage on the DMM match the voltage indicated?</P></TD>
<TD vAlign=center align=middle>


0V</P></TD>
<TD vAlign=bottom align=middle>


Go to Step5 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step7 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S05>


5</P></A></TD>
<TD>

1. <LI type=1>With a DMM, measure voltage by probing the motor controlB
   circuit and use the other lead to probe one of the four encoder signal circuits.
   
   <LI type=1>With a scan tool, command motorB driver low ON. </LI>

Does the DMM indicate voltage within the specified range?</P></TD>
<TD vAlign=center align=middle>


4.3-4.7V</P></TD>
<TD vAlign=bottom align=middle>


Go to Step6 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step8 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S06>


6 </P></A></TD>
<TD>


With a DMM, check motor controlA and motor controlB circuits for
being shorted together.</P>


Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step9 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S07>


7</P></A></TD>
<TD vAlign=top align=left>


With a DMM, check the motor controlA circuit for a short to ground,
short to voltage, open, or high resistance.</P>


Refer to <A
href="/servlets/CellHandler?CellId=62194&RefDoc=841813&evc=sm">Cir cuit
Testing</A> and <A
href="/servlets/CellHandler?CellId=61965&RefDoc=841813&evc=sm">Wir ing
Repairs</A> in Wiring Systems.</P>


Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step10 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S08>


8 </P></A></TD>
<TD vAlign=top align=left>


With a DMM, check the motor controlB circuit for a short to ground,
short to voltage, open, or high resistance.</P>


Refer to <A
href="/servlets/CellHandler?CellId=62194&RefDoc=841813&evc=sm">Cir cuit
Testing</A> and <A
href="/servlets/CellHandler?CellId=61965&RefDoc=841813&evc=sm">Wir ing
Repairs</A> in Wiring Systems.</P>


Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step10 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S09>


9</P></A></TD>
<TD vAlign=top align=left>


Replace the encoder motor. Refer to <A
href="/servlets/CellHandler?CellId=69993&RefDoc=841813&evc=sm">Tra nsfer
Case Motor/Encoder Replacement</A> .</P>


Did you complete the repair?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11 </P></TD>
<TD vAlign=center align=middle>


--</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S10>


10</P></A></TD>
<TD vAlign=top align=left>


Replace the transfer case shift control module. Refer to <A
href="/servlets/CellHandler?CellId=69989&RefDoc=841813&evc=sm">Tra nsfer
Case Shift Control Module Replacement</A> .</P>


Did you complete the repair?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11 </P></TD>
<TD vAlign=center align=middle>


--</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S11>


11</P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Use the scan tool in order to clear the DTCs.
   <LI type=1>Operate the vehicle within the Conditions for Setting the DTC as
   specified in the supporting text. </LI>

Does the DTC reset?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step2</P></TD>
<TD vAlign=center align=middle>


System OK</P></TD></TR></TBODY></TABLE>
<FORM name=bottomNavForm>
<HR>
</FORM></A>

[PARAGON]

<H1>DTC C0327</H1><A name=ss1-853460><A href="#ss1-853460">
<H5>Circuit Description</A></H5>


The transfer case shift control module has four encoder channels, P, C, A,
and B, which are supplied 5volts each. The four encoder channels each run
to a switch located inside the encoder/motor assembly. When a particular encoder
channel is active the switch is closed and 5volts flows through the
encoder signal return circuit. If the module wants to request motor position a
low side driver pulls the voltage low on the encoder signal return and the
corresponding channel circuit indicating motor position.</P>


The transfer case shift control module supplies 5volts on all encoder
channels, thus as these channels are pulled to ground, the module can interpret
the location of the transfer case shift position.</P>


This DTC detects an open, high resistance, or a short to voltage in the
encoder signal return circuit, or an open, high resistance, or short to voltage
in the encoder channel circuits.</P><A name=ss2-853460><A href="#ss2-853460">
<H5>Conditions for Running the DTC</A></H5>
<UL type=BULLET>
<LI>Ignition is ON.
<LI>System voltage is 9--18volts. </LI>[/list]<A name=ss3-853460><A
href="#ss3-853460">
<H5>Conditions for Setting the DTC</A></H5>


The transfer case shift control module reads back a high voltage when a low
voltage is expected, or low voltage when a high voltage is expected on the
encoder channel circuits, or the encoder signal return circuit.</P><A
name=ss4-853460><A href="#ss4-853460">
<H5>Action Taken When the DTC Sets</A></H5>
<UL type=BULLET>
<LI>All motor activity will stop.
<LI>All the transfer case shift control switch mode indicators will be commanded
OFF.
<LI>The SERVICE 4WD indicator will be latched on for the remainder of the
current ignition cycle.
<LI>If a new mode is requested while the DTC is present either current or
history, the indicator for the mode requested will flash for 15seconds and
then go out. </LI>[/list]<A name=ss5-853460><A href="#ss5-853460">
<H5>Conditions for Clearing the DTC</A></H5>
<UL type=BULLET>
<LI>The transfer case shift control module will clear the DTC if the condition
for setting the DTC no longer exists.
<LI>A history DTC will clear after 33consecutive ignition cycles without a
fault present.
<LI>History DTCs can be cleared using a scan tool. </LI>[/list]<A
name=ss6-853460><A href="#ss6-853460">
<H5>Test Description</A></H5>


The numbers below refer to the step numbers on the diagnostic table.</P>

1. <A name=TD02>
   <LI value=2>
   
   
   Determines if two or more of the 5volts encoder signal circuits are
   shorted together.</P><A name=TD03>
   <LI value=3>
   
   
   Checks for proper voltage on the four encoder signal circuits.</P><A
   name=TD04>
   <LI value=4>
   
   
   Tests for a short to voltage, open, or high resistance on the encoder low
   reference circuit.</P><A name=TD05>
   <LI value=5>
   
   
   Determines which encoder signal circuits are shorted together.</P><A
   name=TD06>
   <LI value=6>
   
   
   Determines if any of the encoder signal circuits have an open, or high
   resistance condition.</P><A name=TD07>
   <LI value=7>
   
   
   Determines if a binding shift detent lever shaft is causing the
   DTC.</P></LI>

<TABLE width="100%" border=1>
<TBODY>
<TR>
<TH vAlign=bottom align=middle>


Step</P></TH>
<TH vAlign=bottom align=middle>


Action</P></TH>
<TH vAlign=bottom align=middle>


Value(s)</P></TH>
<TH vAlign=bottom align=middle>


Yes</P></TH>
<TH vAlign=bottom align=middle>


No</P></TH></TR>
<TR>
<TD vAlign=bottom colSpan=5>


Schematic Reference: <A
href="/servlets/CellHandler?CellId=69955&RefDoc=853460&evc=sm">Tra nsfer
Case Control Schematics</A> </P>


Connector End View Reference: <A
href="/servlets/CellHandler?CellId=69957&RefDoc=853460&evc=sm">Tra nsfer
Case Control Connector End Views</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S01>


1</P></A></TD>
<TD vAlign=top align=left>


Did you perform the Diagnostic System Check - Transfer Case?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step2</P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=69959&RefDoc=853460&evc=sm">Dia gnostic
System Check - Transfer Case</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S02>


2</P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Set the parking brake.
   <LI type=1>Raise the vehicle on a hoist.
   <LI type=1>Disconnect the connector at the transfer case.
   <LI type=1>Turn the ignition ON, with the engine OFF.
   <LI type=1>Install a scan tool.
   <LI type=1>While monitoring the encoder channels on the scan tool, short to
   ground each of the encoder channel circuits on the module side of the harness
   with a jumper wire. </LI>

Do more than one of the four encoder channels indicate OFF when each encoder
channel circuit is individually shorted to ground?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step5</P></TD>
<TD vAlign=bottom align=middle>


Go to Step3</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S03>


3</P></A></TD>
<TD vAlign=top align=left>


At the transfer case connector, using a DMM, test the encoder signal circuits
on the module side of the harness.</P>


Are the voltages within the specified range?</P></TD>
<TD vAlign=center align=middle>


4.3-4.7V</P></TD>
<TD vAlign=bottom align=middle>


Go to Step4</P></TD>
<TD vAlign=bottom align=middle>


Go to Step6</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S04>


4</P></A></TD>
<TD vAlign=top align=left>


With the ignition in the OFF position, test the encoder low reference circuit
for a short to ground, short to voltage, open, or high resistance. Refer to <A
href="/servlets/CellHandler?CellId=62194&RefDoc=853460&evc=sm">Cir cuit
Testing</A> and <A
href="/servlets/CellHandler?CellId=61965&RefDoc=853460&evc=sm">Wir ing
Repairs</A> in Wiring Systems.</P>


Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11</P></TD>
<TD vAlign=bottom align=middle>


Go to Step7</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S05>


5 </P></A></TD>
<TD>

1. <LI type=1>Disconnect C1 and C2 from the transfer case shift control module.
   <LI type=1>Using a DMM, check for two or more encoder signal circuits being
   shorted together. Refer to <A
   href="/servlets/CellHandler?CellId=62194&RefDoc=853460&evc=sm">Cir cuit
   Testing</A> and <A
   href="/servlets/CellHandler?CellId=61965&RefDoc=853460&evc=sm">Wir ing
   Repairs</A> in Wiring Systems. </LI>

Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11</P></TD>
<TD vAlign=bottom align=middle>


Go to Step10</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S06>


6 </P></A></TD>
<TD vAlign=top align=left>


Test the suspect circuits for a short to ground, short to voltage, open, or
high resistance. Refer to <A
href="/servlets/CellHandler?CellId=62194&RefDoc=853460&evc=sm">Cir cuit
Testing</A> and <A
href="/servlets/CellHandler?CellId=61965&RefDoc=853460&evc=sm">Wir ing
Repairs</A> in Wiring Systems.</P>


Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11</P></TD>
<TD vAlign=bottom align=middle>


Go to Step10</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S07>


7</P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Remove the encoder motor.
   <LI type=1>Inspect the shift detent lever shaft for a binding condition. Refer
   to <A
   href="/servlets/CellHandler?CellId=69993&RefDoc=853460&evc=sm">Tra nsfer
   Case Motor/Encoder Replacement</A> . </LI>

Did the shift detent lever shaft bind?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step8</P></TD>
<TD vAlign=bottom align=middle>


Go to Step9</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S08>


8</P></A></TD>
<TD vAlign=top align=left>


Remove the transfer case for disassembly and repair. Refer to <A
href="/servlets/CellHandler?CellId=72537&RefDoc=853460&evc=sm">Tra nsfer
Case Disassemble</A> .</P>


Did you complete the repair?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11</P></TD>
<TD vAlign=center align=middle>


--</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S09>


9</P></A></TD>
<TD vAlign=top align=left>


Replace the encoder motor. Refer to <A
href="/servlets/CellHandler?CellId=69993&RefDoc=853460&evc=sm">Tra nsfer
Case Motor/Encoder Replacement</A> .</P>


Did you complete the repair?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11</P></TD>
<TD vAlign=center align=middle>


--</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S10>


10</P></A></TD>
<TD vAlign=top align=left>


Replace the transfer case shift control module. Refer to <A
href="/servlets/CellHandler?CellId=69989&RefDoc=853460&evc=sm">Tra nsfer
Case Shift Control Module Replacement</A> .</P>


Did you complete the repair?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step11</P></TD>
<TD vAlign=center align=middle>


--</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S11>


11</P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Use the scan tool in order to clear the DTCs.
   <LI type=1>Operate the vehicle within the Conditions for Running the DTC as
   specified in the supporting text. </LI>

Does the DTC set?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step1</P></TD>
<TD vAlign=bottom align=middle>


System OK</P></TD></TR></TBODY></TABLE>
<FORM name=bottomNavForm>
<HR>
</FORM></A>

[PARAGON]

<H1>DTC C0329</H1><A name=ss1-857757><A href="#ss1-857757">
<H5>Circuit Description</A></H5>


The transfer case shift control module has four encoder channels coming out
of it which are all supplied 5volts. These four channels are P, C, A, and
B, each running to a switch located inside the encoder/motor assembly. When a
particular encoder channel is active, the switch is closed and 5volts
flows through the encoder signal return circuit. If the module wants to request
motor position, a low side driver pulls the voltage low on the encoder signal
return and the corresponding channel circuit indicating motor position.</P>


The transfer case shift control module supplies 5volts on all the
channels As these channels are pulled to ground, the module can interpret the
location of the transfer case shift position.</P>


This DTC detects a short to ground in the encoder signal return circuit, or a
short to ground in the encoder channel circuits.</P><A name=ss2-857757><A
href="#ss2-857757">
<H5>Conditions for Running the DTC</A></H5>
<UL type=BULLET>
<LI>Ignition is ON.
<LI>System voltage is 9-18volts. </LI>[/list]<A name=ss3-857757><A
href="#ss3-857757">
<H5>Conditions for Setting the DTC</A></H5>


The transfer case shift control module can command the low side driver on the
encoder signal return circuit not to pull the signal low. The module can then
read the voltage on each of the encoder channel circuits. If the voltage is low
a short to ground is indicated and the DTC is logged.</P><A name=ss4-857757><A
href="#ss4-857757">
<H5>Action Taken When the DTC Sets</A></H5>
<UL type=BULLET>
<LI>All motor activity will stop.
<LI>All the transfer case shift control switch mode indicators will be commanded
OFF.
<LI>The SERVICE 4WD indicator will be commanded ON, and an active DTC set, when
a shift is requested.
<LI>If a shift is not being requested the DTC will go to history.
<LI>If a new mode is requested while the DTC is present either current or
history, the indicator for the mode requested will flash for 15seconds and
then go out. </LI>[/list]<A name=ss5-857757><A href="#ss5-857757">
<H5>Conditions for Clearing the DTC</A></H5>
<UL type=BULLET>
<LI>The transfer case shift control module will clear the DTC if the condition
for setting the DTC no longer exists.
<LI>A history DTC will clear after 33consecutive ignition cycles without a
fault present.
<LI>History DTCs can be cleared using a scan tool. </LI>[/list]<A
name=ss6-857757><A href="#ss6-857757">
<H5>Test Description</A></H5>


The numbers below refer to the step numbers on the diagnostic table.</P>

1. <A name=TD02>
   <LI value=2>
   
   
   This step determines if one or more of the encoder channel circuits are
   shorted to ground.</P><A name=TD03>
   <LI value=3>
   
   
   This step checks with a DMM for a short to ground on any of the four encoder
   channel circuits.</P><A name=TD04>
   <LI value=4>
   
   
   This step checks the encoder sign return circuit for a short to ground.</P><A
   name=TD05>
   <LI value=5>
   
   
   This step determines if a faulty transfer case shift control module is
   causing the DTC to set.</P><A name=TD06>
   <LI value=6>
   
   
   This step determines if the encoder motor is causing the DTC to
   set.</P></LI>

<TABLE width="100%" border=1>
<TBODY>
<TR>
<TH vAlign=bottom align=middle>


Step</P></TH>
<TH vAlign=bottom align=middle>


Action</P></TH>
<TH vAlign=bottom align=middle>


Value(s)</P></TH>
<TH vAlign=bottom align=middle>


Yes</P></TH>
<TH vAlign=bottom align=middle>


No</P></TH></TR>
<TR>
<TD vAlign=bottom align=left colSpan=5>


Schematic Reference: <A
href="/servlets/CellHandler?CellId=69955&RefDoc=857757&evc=sm">Tra nsfer
Case Control Schematics</A> </P>


Connector End View Reference: <A
href="/servlets/CellHandler?CellId=69957&RefDoc=857757&evc=sm">Tra nsfer
Case Control Connector End Views</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S01>


1</P></A></TD>
<TD vAlign=top align=left>


Did you perform the Diagnostic System Check - Transfer Case?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step2 </P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=69959&RefDoc=857757&evc=sm">Dia gnostic
System Check - Transfer Case</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S02>


2 </P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Set the parking brake.
   <LI type=1>Raise the vehicle on a hoist.
   <LI type=1>Disconnect the connector at the transfer case.
   <LI type=1>Turn the ignition ON, with the engine OFF.
   <LI type=1>Install a scan tool.
   <LI type=1>Monitor the encoder channels P, B, A, and C on the scan tool.
   </LI>

Do any of the encoder channels indicate OFF.</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step3 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step4 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S03>


3 </P></A></TD>
<TD vAlign=top align=left>


Test the encoder channel circuit that is indicating OFF on the scan tool for
a short to ground. Refer to <A
href="/servlets/CellHandler?CellId=62194&RefDoc=857757&evc=sm">Cir cuit
Testing</A> and <A
href="/servlets/CellHandler?CellId=61965&RefDoc=857757&evc=sm">Wir ing
Repairs</A> in Wiring Systems.</P>


Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step9 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step8 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S04>


4 </P></A></TD>
<TD vAlign=top align=left>


With the ignition in the OFF position, test the encoder low reference circuit
for a short to ground. Refer to <A
href="/servlets/CellHandler?CellId=62194&RefDoc=857757&evc=sm">Cir cuit
Testing</A> and <A
href="/servlets/CellHandler?CellId=61965&RefDoc=857757&evc=sm">Wir ing
Repairs</A> in Wiring Systems.</P>


Did you find and correct the condition?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step9 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step5 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S05>


5 </P></A></TD>
<TD>

1. <LI type=1>Turn the ignition ON with the engine OFF.
   <LI type=1>With the transfer case connector still disconnected, use the scan
   tool to clear DTCs. </LI>

Does DTC C0329 reset?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step8 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step6 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S06>


6 </P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Turn the ignition OFF.
   <LI type=1>Connect the transfer case connector.
   <LI type=1>Turn the ignition ON, with the engine OFF.
   <LI type=1>With the transfer case shift control switch, command the transfer
   case through all of the modes.
   <LI type=1>Using a scan tool, check DTCs. </LI>

Does DTC C0329 set?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step7 </P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=62111&RefDoc=857757&evc=sm">Tes ting
for Electrical Intermittents</A> in Wiring Systems </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S07>


7</P></A></TD>
<TD vAlign=top align=left>


Replace the encoder motor. Refer to <A
href="/servlets/CellHandler?CellId=69993&RefDoc=857757&evc=sm">Tra nsfer
Case Motor/Encoder Replacement</A> .</P>


Did you complete the repair?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step9 </P></TD>
<TD vAlign=bottom align=middle>


--</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S08>


8</P></A></TD>
<TD vAlign=top align=left>


Replace the transfer case shift control module. Refer to <A
href="/servlets/CellHandler?CellId=69989&RefDoc=857757&evc=sm">Tra nsfer
Case Shift Control Module Replacement</A> .</P>


Did you complete the repair?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step9 </P></TD>
<TD vAlign=bottom align=middle>


--</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S09>


9</P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Use the scan tool in order to clear the DTCs.
   <LI type=1>Operate the vehicle within the Conditions for Running the DTC as
   specified in the supporting text. </LI>

Does the DTC set?</P></TD>
<TD vAlign=center align=middle>


--</P></TD>
<TD vAlign=bottom align=middle>


Go to Step1 </P></TD>
<TD vAlign=bottom align=middle>


System OK</P></TD></TR></TBODY></TABLE>
<FORM name=bottomNavForm>
<HR>
</FORM></A>

[PARAGON]

<H1>DTC C0550</H1><A name=ss1-830462><A href="#ss1-830462">
<H5>Circuit Description</A></H5>


At each power-up the transfer case shift control module runs a self-test on
the following functions:</P>
<UL type=BULLET>
<LI>EEPROM Checksum
<LI>ROM Checksum
<LI>RAM Checksum
<LI>RAM Malfunction </LI>[/list]<A name=ss2-830462><A href="#ss2-830462">
<H5>Conditions for Running the DTC</A></H5>
<UL type=BULLET>
<LI>Ignition is ON.
<LI>System voltage is 9-18volts. </LI>[/list]<A name=ss3-830462><A
href="#ss3-830462">
<H5>Conditions for Setting the DTC</A></H5>
<UL type=BULLET>
<LI>Critical operational parameters stored in EEPROM have failed Checksum test
indicating invalid data.
<LI>Masked ROM code has failed Checksum test indicating that masked ROM data is
not currently valid.
<LI>ROM code has failed Checksum test indicating that ROM data is not currently
valid.
<LI>One or more ROM locations have failed operational test indicating that some
portions of RAM are not functional. </LI>[/list]<A name=ss4-830462><A
href="#ss4-830462">
<H5>Action Taken When the DTC Sets</A></H5>
<UL type=BULLET>
<LI>The SERVICE 4WD indicator will be latched on and the system will be
disabled.
<LI>The transfer case control switch will display the current position LED while
DTC C0550 is current, but further shifting will be disabled. </LI>[/list]<A
name=ss5-830462><A href="#ss5-830462">
<H5>Conditions for Clearing the DTC</A></H5>
<UL type=BULLET>
<LI>Replace the transfer case shift control module.
<LI>Perform the Transfer Case Diagnostic System Check. </LI>[/list]<A
name=ss6-830462><A href="#ss6-830462">
<H5>Test Description</A></H5>


The number below refers to the step number on the diagnostic table.</P>

1. <A name=TD02>
   <LI value=2>
   
   
   Replacement of the transfer case shift control module.</P></LI>

<TABLE width="100%" border=1>
<TBODY>
<TR>
<TH vAlign=bottom align=middle>


Step</P></TH>
<TH vAlign=bottom align=middle>


Action</P></TH>
<TH vAlign=bottom align=middle>


Yes</P></TH>
<TH vAlign=bottom align=middle>


No</P></TH></TR>
<TR>
<TD vAlign=bottom colSpan=4>


Schematic Reference: <A
href="/servlets/CellHandler?CellId=69955&RefDoc=830462&evc=sm">Tra nsfer
Case Control Schematics</A> </P>


Connector End View Reference: <A
href="/servlets/CellHandler?CellId=69957&RefDoc=830462&evc=sm">Tra nsfer
Case Control Connector End Views</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S01>


1</P></A></TD>
<TD vAlign=top align=left>


Did you perform the Diagnostic System Check-Transfer Case?</P></TD>
<TD vAlign=bottom align=middle>


Go to Step2 </P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=69959&RefDoc=830462&evc=sm">Dia gnostic
System Check - Transfer Case</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S02>


2 </P></A></TD>
<TD vAlign=top align=left>


Replace the transfer case shift control module. Refer to <A
href="/servlets/CellHandler?CellId=69989&RefDoc=830462&evc=sm">Tra nsfer
Case Shift Control Module Replacement</A> .</P>


Is the repair complete?</P></TD>
<TD vAlign=bottom align=middle>


System OK</P></TD>
<TD vAlign=bottom align=middle>


--</P></TD></TR></TBODY></TABLE>
<FORM name=bottomNavForm>
<HR>
</FORM></A>

[PARAGON]

<H1>Diagnostic System Check - Transfer Case</H1>


These diagnostic procedures will help you to find and repair full time 4WD
transfer case (FT4WD) system malfunctions. This service category also contains
information for repairing FT4WD system malfunctions. For best results, use the
diagnostic tables, and follow the sequence listed below:</P>

1. <LI type=1>Perform the Transfer Case Diagnostic System Check. All FT4WD
   diagnostics must begin with the Transfer Case Diagnostic System Check. The
   Transfer Case Diagnostic System Check determines the following:
   <UL type=BULLET>
   <LI>Proper SERVICE 4WD indicator operation.
   <LI>Ability of the transfer case shift control module to communicate through the
   data link connector (DLC)
   <LI>Existence of FT4WD DTCs </LI>

<LI type=1>Refer to the diagnostic table as directed by the Transfer Case
Diagnostic System Check. The diagnostic tables will help enable you to diagnose
any FT4WD system malfunction. Bypassing these procedures may result in the
following:
<UL type=BULLET>
<LI>Extended Diagnostic Time
<LI>Incorrect Diagnosis
<LI>Incorrect Parts Replacement </LI>[/list]<LI type=1>Repeat the Transfer Case Diagnostic System Check after you perform
any repair or diagnostic procedures. This will verify that you correctly
performed the repair. This will also ensure that other malfunctions do not
exist. </LI>[/list]<A name=ss1-836901><A href="#ss1-836901">
<H5>Test Description</A></H5>


The numbers below refer to the step numbers on the diagnostic table.</P>

1. <A name=TD02>
   <LI value=2>
   
   
   Lack of communication may be due to a partial malfunction of the class2
   serial data circuit or due to a total malfunction of the class2 serial
   data circuit. The specified procedure will determine the particular
   condition.</P><A name=TD03>
   <LI value=3>
   
   
   A fuse failure will cause no communication this step has you check for this
   condition.</P><A name=TD04>
   <LI value=4>
   
   
   This step determines if the fuse blows when the ignition is turned on.</P><A
   name=TD05>
   <LI value=5>
   
   
   This step determines if there is a short to ground in the battery positive
   circuit causing the fuse to blow.</P><A name=TD06>
   <LI value=6>
   
   
   This step refers to the table for DTCC0306 for further diagnosis if a
   transfer case mode change is causing the fuse to blow.</P><A name=TD07>
   <LI value=7>
   
   
   The presence of DTCs indicates that the transfer case shift control module
   has detected a fault. Go to symptoms for other concerns.</P><A name=TD08>
   <LI value=8>
   
   
   The presence of DTCs which begin with "U" indicate some other module is not
   communicating. The specified procedure will compile all the available
   information before tests are performed.</P><A name=TD09>
   <LI value=9>
   
   
   Vehicle speed is provided to the transfer case shift control module via
   Class2 and can effect the setting of DTC C0300. Perform the diagnostics
   for powertrain DTCs P0502 and P0503 first.</P></LI>

<TABLE width="100%" border=1>
<TBODY>
<TR>
<TH vAlign=bottom align=middle>


Step</P></TH>
<TH vAlign=bottom align=middle>


Action</P></TH>
<TH vAlign=bottom align=middle>


Yes</P></TH>
<TH vAlign=bottom align=middle>


No</P></TH></TR>
<TR>
<TD vAlign=center align=middle><A name=S01>


1</P></A></TD>
<TD vAlign=top align=left>


Install a scan tool.</P>


Does the scan tool power up?</P></TD>
<TD vAlign=bottom align=middle>


Go to Step2 </P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=11032&RefDoc=836901&evc=sm">Sca n Tool
Does Not Power Up</A> in Data Link Communications</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S02>


2 </P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Turn ON the ignition, with the engine OFF.
   <LI type=1>Attempt to establish communication with the transfer case shift
   control module. </LI>

Does the scan tool communicate with the transfer case shift control
module?</P></TD>
<TD vAlign=bottom align=middle>


Go to Step7 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step3 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S03>


3 </P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Turn off the ignition.
   <LI type=1>Check the underhood TREC fuse. </LI>

Did the TREC fuse blow?</P></TD>
<TD vAlign=bottom align=middle>


Go to Step4 </P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=11033&RefDoc=836901&evc=sm">Sca n Tool
Does Not Communicate with Class 2 Device</A> in Data Link
Communications</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S04>


4 </P></A></TD>
<TD vAlign=top align=left>


Replace the TREC fuse.</P>


Does the ATC fuse blow immediately?</P></TD>
<TD vAlign=bottom align=middle>


Go to Step5 </P></TD>
<TD vAlign=bottom align=middle>


Go to Step6 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S05>


5 </P></A></TD>
<TD vAlign=top align=left>


Check the battery positive circuit for a short to ground.</P>


Was the condition found and corrected?</P></TD>
<TD vAlign=bottom align=middle>


Go to Step2 </P></TD>
<TD vAlign=bottom align=middle>


Go to Transfer Case Shift Control Module Replacement.</P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S06>


6 </P></A></TD>
<TD vAlign=top align=left>

1. <LI type=1>Start the Engine
   <LI type=1>Attempt to shift the transfer case to different modes.
   <LI type=1>Check the underhood TREC fuse. </LI>

Did the TREC fuse blow?</P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=69972&RefDoc=836901&evc=sm">DTC
C0306</A> </P></TD>
<TD vAlign=bottom align=middle>


Go to Step2 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S07>


7 </P></A></TD>
<TD vAlign=top align=left>


Select the transfer case shift control module display DTCs function on the
scan tool.</P>


Does the scan tool display any DTCs?</P></TD>
<TD vAlign=bottom align=middle>


Go to Step8 </P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=69979&RefDoc=836901&evc=sm">Sym ptoms
- Transfer Case</A> </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S08>


8 </P></A></TD>
<TD vAlign=top align=left>


Does the scan tool display any DTCs which begin with a "U"?</P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=11033&RefDoc=836901&evc=sm">Sca n Tool
Does Not Communicate with Class 2 Device</A> in Data Link
Communications</P></TD>
<TD vAlign=bottom align=middle>


Go to Step9 </P></TD></TR>
<TR>
<TD vAlign=center align=middle><A name=S09>


9 </P></A></TD>
<TD vAlign=top align=left>


Does the scan tool display DTCP0502 or P0503?</P></TD>
<TD vAlign=bottom align=middle>


Go to Applicable Powertrain OBD Diagnostic System Check</P></TD>
<TD vAlign=bottom align=middle>


Go to <A
href="/servlets/CellHandler?CellId=69963&RefDoc=836901&evc=sm">Dia gnostic
Trouble Code (DTC) List</A> </P></TD></TR></TBODY></TABLE>
<FORM name=bottomNavForm>
<HR>
</FORM></A>

[2-H2's]

Thank You Wise One...

Where or how does one obtain such useful info.? Is it availavble to the general public?

I needs this info

I dispise going to the dealer!!!

You da man...

LC

[HUMTECH]

Your best bet would be to buy an OBD II code reader available at most auto parts stores, then you could post the code here and there are several members with full access to the si service manuals including me. SI is not readily available to the public but A paper service manual could be obtained from the dealer but if I remember they are quite pricy.

[MarineHawk]

Originally posted by PARAGON:
The transfer case motor is a bi-directional ...

Like Hillary Clinton and Melissa Etheridge?

[2-H2's]

Thank You gentlemen...

I'll find something out Monday & get me one of them there copies of SI. I'd better not see one tomorrow or it might just disappear

HT where in Canada...i'll be in SK this week & later in the month.

Phil, I know it's Sunday & all, but did you get my email containing our new wants?

LC

[2-H2's]

Looks like it's a "Hummer" problem & not a mod issue...

I'm still at the dealer, should know more in another hour. I'm very impressed with the professionalism I have received today.

LC

[2-H2's]

It appears that a ground wire had worked itself loose under the steering wheel. There are three plugs in a cluster, the center one was the one causing the headaches. Once the wire was attached properly & the computer reset...walla...four wheel driving again!!!

I'll have to say the dealer was very courteous today & handled everything to my satisfaction. And yes it was covered under the warranty. Yee-Haw

LC