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2-42 Service Manual
5016-001
Coupling Unit Service Check
A 990 Service Engine Error. The coupling does not turn.
B 990 Service Engine Error. The coupling motor turns.
C 991 Service Engine Error. Indicates a problem with the coupling
on and off sensors.
Note: Verify correct operation of the mechanical parts of the
coupling unit by manually resetting the coupling unit. Use the green
coupling arm knob to reset the coupling unit and observe its
operation.
A 990 Service Engine Error - Motor does not turn on.
FRU Action
1 Coupling Motor
Cable MK2
Engine Board
Disconnect the coupling motor at the inline
connector and measure the resistance of the
motor on the motor connector. It should
measure between 9 and 15 ohms. If incorrect,
replace the motor.
The motor may be binding due to a problem in
the motor mounting stay assembly. Remove the
stay assembly and check for problems with the
motor and coupling unit. Repair as necessary.
If no problem is found and the motor does not
turn, check cable MK2.
• If incorrect, replace the cable.
• If correct, replace the engine board.