<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>
- <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>
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