(e)  
Press MENU to return to the main menu.

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C.  Fault History provides detail information about faults that occurred prior to the last power cycle. A power cycle is the time between power being applied to the plane and the power being disconnected.
(1)  
Ensure that the YDC BITE panel displays EXISTING FAULTS? from the main menu. If necessary, press MENU until the main menu appears and scroll using up or down arrows until EXISTING FAULTS? is displayed. 

(2)  
Press the down arrow and observe that FAULT HISTORY? displays on the panel.

(3) 
 Press YES.

(a)  
If there are no faults in Fault History, NO FAULT HISTORY will display on the panel.

(b)  
If any faults are present in Fault History, CYCLE N? will display on the panel. N is the number of the last power cycle to incur a fault. 1) To view fault details for this cycle, press YES.

a) The panel will display the faults that occurred during the cycle.  b) To view fault details, follow the procedures to view faults as shown in 3(a) thru 3(a)-4.
NOTE:  Four lines of data are displayed in the MORE DETAILS? screen. Line 1 - Message Number Line 2 - Flight Deck Effect Line 3 - LRU(s) responsible for the fault Line 4 - Fault was hard or intermittent.
c)  To view other faults, press the down arrow, observe that MORE DETAILS? displays on the panel, and then press NO.
(c)  
To view other power cycles, press menu until CYCLE X is displayed (where X is the last cycle displayed). Press the down arrow to display the next power cycle with a fault.

(d)  
If END OF LIST is displayed on the panel, no further power cycles exist in the Fault History.

D.  Ground Tests
(1)  
Perform Check Self-Test Switches and Warning Lights (Ref 22-12-01)

(2)  
Perform Yaw Damper Configuration and System Tests (Ref 22-12-01)

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Fault  Fault Detail  Fault Detail  Fault Detail  Fault Detail  Fault Detail  Isolation procedure 
Message  1  2  3  4a  4b 
(Existing Faults/  (Fault 
Ground Test  History) 
Fault Display) 
Internal YDC faults requiring or resulting from YDC Self Test 
YDC fault  msg. no. 22-21000  FDE: YD disenga  YDC  LATCHED: Note 3  TYPE: Note 2  Possible Causes: . Yaw damper coupler Troubleshooting: . Pressurize A and B system hydraulics. . Perform the yaw damper coupler installation test, ref AMM12-12-01, page 401 step 4. . If the problem persists, replace the yaw damper coupler. 
Internal YDC faults requiring or resulting from Servo Test 
YDC YD  msg. no.  FDE:  YDC  LATCHED:  TYPE: Note  Possible Causes: 
fault  22-21001  YD disenga  Note 3  2  . Yaw damper coupler Troubleshooting: . Pressurize A and B system hydraulics. . Perform the yaw damper coupler installation test, ref AMM12-12-01, page 401 step 4. . If the problem persists, replace the yaw damper coupler. 
Internal YDC faults requiring or resulting from Pressure Reducer Test 
YDC  msg. no.  YDC  LATCHED:  TYPE:  Possible Causes: 
PR fault  22-21002  Note 3  Note 2  . Yaw damper coupler Troubleshooting: . Perform the yaw damper coupler installation test, ref AMM12-12-01, page 401 step 4. . If the problem persists, replace the yaw damper coupler. 
YD engage solenoid faults 
YD sol  msg. No.  FDE:  YD sol  LATCHED:  TYPE:  Possible Causes: 
fault  22-21003  YD disenga  /wrg/YD C  Note 3  Note 2  . Rudder power control unit actuator solenoid . Yaw damper coupler 
Troubleshooting: . Verify resistance from D295 socket 20 to ground is 60 ohms. . Verify wiring between D295 socket 20 and D291 socket 1 at the rudder power control unit actuator solenoid. . Verify connection to ground from D291 socket 2 at the rudder power control unit actuator solenoid. . Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, replace the rudder power control unit. . If problem persists, replace the yaw damper coupler. 

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