ELECTRICAL AND ECU
Component Tests
12-12
BY Service Manual
© 2009 Yanmar Marine International
Figure 12-5 shows a general schematic diagram of
all ECU input and output assignments.
The ECU is supplied by Bosch and has a hardware
specification of EDC 16. The base ECU software is
Bosch DDE 5. The engine control software is
application specific version NSW 400, which is a
torque-based software structure. It is NMEA 2000
implemented and provides diagnostics through
OBD protocol.
The ECU monitors data from the various sensors
and controls such functions as low-pressure fuel
pump operation, fuel injection pressure, fuel
injection system volume, and the timing and volume
of fuel injected by the Bosch electronic fuel
injectors. Throttle control is fly-by-wire, meaning it
is controlled by electric signals from the helm. The
throttle control is either analog or digital depending
on the level of control options installed.
The ECU also uses sensor inputs to monitor engine
condition and will generate a trouble code if a
system or sensor indicates a problem. In most
cases, a Check Engine light will be displayed. The
engine may or may not run normally depending on
the fault. If an engine coolant overheat is detected,
for instance, the ECU will reduce the engine power
output and the coolant overheat indicator will
illuminate. If an audible alarm is installed, it too will
sound.
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
NOTICE: When using a common automotive test
lamp to test relays and their circuits, contact with
terminal 85 (Figure 12-6, (2)) 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 224, the winding ground circuit
(terminal 85) is completed at ECU terminal 234
(assuming neutral is sensed at ECU terminal 250)
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.
Note: Viewed from bottom of connector.
Figure 12-6
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
000417
3
