Variable Signals

TM 5-6675-250-34

(a) Bias mode, pin f (pre-amp output): This

(2) If a malfunction occurs, monitor the signals

should be an ac signal riding on + 9 vdc component.

in that column, following the numerical order shown,

If there is no ac signal, this indicates that the failure

(3) Note in order, all signals which are not

i s in the GRU. To verify this condition, open the

correct.

toggle switch for pin f on the breakout box and check

(4) Repeat steps (1) and (2) for all remaining

for the signal at the GRU terminal. If the signal is

c o l u m n s applicable to the signal. In this manner all

p r e s e n t , the failure is in the ECU.

failures will be noted and checked in more than one

(b) F u s e i n t h e E C U b l o w s e a c h t i m e t h e

m o d e of operation.

pendulum is uncaged: Open the toggle switch for pin

( 5 ) The first failure in each column indicates

L on the breakout box. If the fuse does not blow, the

w h i c h unit is malfunctioning. Conditions noted in

uncage switch is a possible failure. Additional tests

t h e failure column indicate a failure in the GRU or

o f signal associated with the uncaging circuit will

ECU.

isolate the fault.

(6) Examples of failure analysis are provided in

the

following

paragraphs.