Component Tests; Relays - Yanmar BY Series Service Manual

ELECTRICAL AND ECU
Not all inputs are monitored by the ECU. Low oil pressure and water in fuel are two examples. Either of
these conditions will result in a warning indicator and possible audible alarm. Low oil pressure will also be
indicated by the oil gauge at the helm.

COMPONENT TESTS

IMPORTANT
When using a common automotive test
lamp to test relays and their circuits, contact
with terminal 85 will cause the relay to
engage. This will result in starter
engagement or fuel pump operation.

Relays

Relays control power to the starter, fuel feed pump,
and main system power.
The winding ground circuit (terminal 85) of all relays
is controlled by the ECU.
Start Relay (K1)
12 V is supplied by fuse F5 to winding terminal 86.
When the start signal from the key switch is seen at
ECU terminal 2/24, the winding ground circuit
(terminal 85) is completed at ECU terminal 2/34
(assuming neutral is sensed at ECU terminal 2/50)
and current passes through terminals 87 and 30 to
energize the starter motor.
Results of Failed Relay
Failure of the relay results in:
• Inability to start engine
If this relay is defective, no P-codes will be
generated.
12-14
Note: Viewed from bottom of connector.
0004173
Figure 12-6
1 – Pin 2 - terminal 87 (not used)
2 – Pin 4 - terminal 85
3 – Pin 5 - terminal 87
4 – Pin 6 - terminal 30
5 – Pin 8 - terminal 86
BY Service Manual
Component Tests