TM 10-3930-669-20 Section IV.  TROUBLESHOOTING 2-10.  INTRODUCTION TO LOGIC TREE TROUBLESHOOTING. a.  Page Layout.  Troubleshooting procedures are divided into logic tree pages and test pages. (1) A logic tree page is always a left-hand page, facing the test page on the right.  The logic tree page provides the sequence of steps required to isolate a fault to a failed component.  All critical information for decision making is on the left-hand page.  Each logic tree page contains the following information: (a) INITIAL SETUP - This box is located only on the first logic tree page of a fault.  INITIAL SETUP lists tools, materials, references, personnel and equipment needed to troubleshoot the fault. (b) KNOWN INFO - This box is located in the top left-hand column.  KNOWN INFO lists conditions and information that will eliminate specific components as the cause of the fault. (c)  POSSIBLE  PROBLEMS  -  This  box  is  located  directly  below  KNOWN  INFO.    All  of  the  system components  that  could  cause  a  fault  are  listed  in  the  POSSIBLE  PROBLEMS  box.    The  first  component  listed  in  the POSSIBLE  PROBLEMS  box  is  the  one  that  will  be  tested  at  that  step  in  the  logic  sequence.  When  one  of  the components is tested and found to be operational, it is entered at the bottom of the KNOWN INFO box as OK. (d) QUESTION - Each question, located in the middle column, refers to the first possible problem listed in POSSIBLE PROBLEMS.  If the answer to the question is YES, proceed to the next step.  If the answer is NO, follow the NO arrow to obtain directions for correcting the problem.  If the step contains a WARNING or CAUTION message, a small  shadow  box  is  printed  above  the  question.    Text  for  WARNINGS  and  CAUTIONS  is  on  the  following  right-hand page. (e) TEST OPTIONS - This box is located directly below TEST OPTIONS.  It explains the purpose for the question in the middle column. (f)  REASON  FOR  QUESTION  -  This  box  is  located  directly  below  TEST  OPTIONS.    It  explains  the purpose for the question in the middle column. (2)  A  test  page  is  always  a  right-hand  page,  facing  the  logic  tree  page  on  the  left.    The  test  provides  detailed instructions  for  testing  the  first  component  listed  in  the  POSSIBLE  PROBLEMS  box.    This  test  will  also  provide  an answer for the question in the middle column.  Note the arrow connecting the test on the right-hand page to the REASON FOR  QUESTION.    When  possible,  illustrations  are  included  to  provide  visual  details.    Warnings,  cautions,  and  notes contain additional information for testing. b.  How to Begin Troubleshooting. (1)  Determine  the  symptom  or  condition  that  indicates  a  problem  or  failure.    Troubleshooting  is  divided  into symptoms peculiar to a system or a component, for example: hydraulic system or engine.  Refer to the Troubleshooting Fault Index (Table 2-3) for a list of the systems covered in this section. (2) Go to the referenced page to begin troubleshooting.  Open the manual flat so both the left-hand and right- hand  pages  are  displayed  before  you.    The  information  on  both  pages  is  important  to  resolve  the  problem  or  failure. However,  the  experienced  technician  can  follow  the  left-hand  page  instructions  and  refer  to  the  right-hand  page  when necessary. (3) Follow the diagnostic procedure.  Answer question No.  1 on the left-hand page and follow the YES or NO path  to  either  the  remedy  or  the  next  question.    If  necessary,  look  on  the  right-hand  page  for  test  instructions  and illustrations. 2-9