Yamaha YZ 2018 Series, Owner'S Service Manual, Page: 341 / 402

FUEL INJECTION SYSTEM
8-42
Fault code No. 43
Item
Fuel system voltage: incorrect voltage supplied to the fuel in-
jector and fuel pump.
Fail-safe system Able to start engine
Able to drive vehicle
Diagnostic code No. 09
Diagnostic tool display Fuel system voltage
Approximately 12.0 (V)
Procedure Disconnect the main relay, and push the start switch.
Item
Probable cause of malfunc-
tion and check
Maintenance job
Confirmation of service
completion
1 Connection of main relay
coupler.
Check the locking condition
of the coupler.
Disconnect the coupler and
check the pins (bent or bro-
ken terminals and locking
condition of the pins). Improperly connected

Connect the coupler securely
or repair/replace the wire har-
ness.
Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 2.
2 Connection of wire harness
ECU coupler.
Check the locking condition
of the coupler.
Disconnect the coupler and
check the pins (bent or bro-
ken terminals and locking
condition of the pins). Improperly connected

Connect the coupler securely
or repair/replace the wire har-
ness.
Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 3.
3 Wire harness continuity. Open or short circuit

Re-
place the wire harness.
Between battery terminal and
ECU coupler.
red-red
red-red/white
Between main relay coupler
and ECU coupler.
brown-brown
blue/red-blue/red
Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 4.
4 Defective main relay. No operating sound

Re-
place the main relay.
Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 5.
5 Defective main relay. Execute the diagnostic mode.
(Code No. 09)
Fuel system voltage is below
3 V

Replace the main re-
lay.
Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 6.
6 Malfunction in ECU. Replace the ECU.