Yamaha Mt 01 T 2005 Manual

							FUEL INJECTION SYSTEM
7-46
Fault code No. 24 Symptom No normal signal is received from the O2 sensor.
Diagnostic code No.——
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Installed state of O
2 sensor. Check for looseness or pinching. Starting the 
engine and 
operating it at 
idle. 2 Connections
O
2 sensor coupler
Main wire harness ECU couplerCheck the coupler for any pins 
that may be pulled out.
Check the locking condition of 
the coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.
3 Open or short circuit in wire harness.Repair or replace if there is an 
open or short circuit.
Between O
2 sensor coupler and 
ECU coupler.
(gray/white–gray/white)
(red/blue–red/blue)
(gray/green–gray/green)
(black/blue–black/blue)
4 Check fuel pressure.Refer to “THROTTLE BODIES” 
on page 6-4.
5 Defective O
2 sensor.Replace if defective. 
						

							FUEL INJECTION SYSTEM
7-47
Fault code No. 25 Symptom Cylinder-#2 intake air pressure sensor: open or short cir-
cuit detected.
Diagnostic code No. 04 Cylinder-#2 intake air pressure sensor
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Connections
Cylinder-#2 intake air pressure 
sensor coupler
Main wire harness ECU couplerCheck the coupler for any pins 
that may be pulled out.
Check the locking condition of 
the coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.Turning the 
main switch to 
“ON”.
2 Open or short circuit in wire harness.Repair or replace if there is an 
open or short circuit.
Between cylinder-#2 intake air 
pressure sensor coupler and 
ECU coupler
(black/blue–black/blue)
(pink/yellow–pink/yellow)
(blue–blue)
3 Defective cylinder-#2 intake air 
pressure sensor.Execute the diagnostic mode. 
(Code No.04)
Replace if defective.
Refer to “CHECKING THE 
INTAKE AIR PRESSURE 
SENSORS” on page 7-106. 
						

							FUEL INJECTION SYSTEM
7-48
Fault code No. 26 Symptom Cylinder-#2 intake air pressure sensor: hose system mal-
function (clogged or detached hose).
Diagnostic code No. 04 Cylinder-#2 intake air pressure sensor
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Cylinder-#2 intake air pressure sensor 
hoseCheck the cylinder-#2 intake air 
pressure sensor hose condition.
Repair or replace the sensor 
hose.Starting the 
engine and 
operating it at 
idle.
2 Cylinder-#2 intake air pressure sensor 
malfunction at intermediate electrical 
potential.Check and repair the 
connection.
Replace it if there is a 
malfunction.
3 Connections
Cylinder-#2 intake air pressure 
sensor coupler
Main wire harness ECU couplerCheck the coupler for any pins 
that may be pulled out.
Check the locking condition of 
the coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.
4 Defective cylinder-#2 intake air 
pressure sensor.Execute the diagnostic mode. 
(Code No.04)
Replace if defective.
Refer to “CHECKING THE 
INTAKE AIR PRESSURE 
SENSORS” on page 7-106. 
						

							FUEL INJECTION SYSTEM
7-49
Fault code No. 28 Symptom Engine temperature sensor: open or short circuit detect-
ed.
Diagnostic code No. 11 Engine temperature sensor
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Installed state of engine temperature 
sensor.Check for looseness or pinching. Turning the 
main switch to 
“ON”.
2 Connections
Engine temperature sensor coupler
Main wire harness ECU coupler
Sub-wire harness 2 couplerCheck the coupler for any pins 
that may be pulled out.
Check the locking condition of 
the coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.
3 Open or short circuit in wire harness 
and/or sub lead.Repair or replace if there is an 
open or short circuit.
Between engine temperature 
sensor coupler and ECU 
coupler
(brown–brown)
(black–black)
4 Defective engine temperature sensor.Execute the diagnostic mode. 
(Code No.11)
Replace if defective.
Refer to “CHECKING THE 
ENGINE TEMPERATURE 
SENSOR” on page 7-102. 
						

							FUEL INJECTION SYSTEM
7-50
Fault code No. 29 Symptom Decompression solenoid (thermistor): open or short cir-
cuit detected.
Diagnostic code No. 55 Decompression solenoid
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Installed state of decompression 
solenoid.Check for looseness or pinching. Turning the 
main switch to 
“ON”.
2 Connections
Decompression solenoid 
(thermistor) coupler
Main wire harness ECU couplerCheck the coupler for any pins 
that may be pulled out.
Check the locking condition of 
the coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.
3 Open or short circuit in wire harness.Repair or replace if there is an 
open or short circuit.
Between decompression 
solenoid (thermistor) coupler 
and ECU coupler
(green/red–green/red)
(black/blue–black/blue)
4 Defective decompression solenoid 
(thermistor).Execute the diagnostic mode. 
(Code No.55)
Replace if defective.
Refer to “CHECKING THE 
DECOMPRESSION 
SOLENOID” on page 7-105.
Fault code No. 30 Symptom The vehicle has overturned.
Diagnostic code No. 08 Lean angle cut-off switch
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 The vehicle has overturned. Raise the vehicle upright. Turning the 
main switch to 
“ON” (however, 
the engine 
cannot be 
restarted 
unless the main 
switch is first 
turned “OFF”). 2 Installed condition of the lean angle 
cut-off switch.Check for looseness or pinching.
3 Connections
Lean angle cut-off switch coupler
Main wire harness ECU couplerCheck the coupler for any pins 
that may be pulled out.
Check the locking condition of 
the coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.
4 Defective lean angle cut-off switch.Execute the diagnostic mode. 
(Code No.08)
Replace if defective.
Refer to “CHECKING THE 
LEAN ANGLE CUT-OFF 
SWITCH” on page 7-100. 
						

							FUEL INJECTION SYSTEM
7-51
Fault  code  No. 33 Symptom Malfunction detected in the primary wire of the cylinder-#1 
left or right ignition coil.
Diagnostic code No. 30, 32 Cylinder-#1 left or right ignition coil
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Connections
Cylinder-#1 left or right ignition coil 
connector (primary coil side)
Main wire harness ECU coupler
Sub-wire harness 1 couplerCheck the connector and 
coupler for any pins that may be 
pulled out.
Check the locking condition of 
the connector and coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.Starting the 
engine and 
operating it at 
idle.
2 Open or short circuit in wire harness 
and/or sub lead.Repair or replace if there is an 
open or short circuit.
Between cylinder-#1 left or right 
ignition coil connector and ECU 
coupler/main wire harness.
(black/red–blue/red)
(orange–orange)
3 Defective cylinder-#1 left or right 
ignition coil.Execute the diagnostic mode. 
(Code No.30 or 32)
Test the primary and secondary 
coils for continuity.
Replace if defective.
Refer to “CHECKING THE 
IGNITION COILS” on page 
7-99. 
						

							FUEL INJECTION SYSTEM
7-52
Fault  code  No. 34 Symptom Malfunction detected in the primary wire of the cylinder-#2 
left ignition coil.
Diagnostic code No. 31 Cylinder-#2 left ignition coil
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Connections
Cylinder-#2 left ignition coil 
connector (primary coil side)
Main wire harness ECU couplerCheck the connector and 
coupler for any pins that may be 
pulled out.
Check the locking condition of 
the connector and coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.Starting the 
engine and 
operating it at 
idle.
2 Open or short circuit in wire harness.Repair or replace if there is an 
open or short circuit.
Between cylinder-#2 left ignition 
coil connector and ECU 
coupler/main wire harness.
(black/red–blue/red)
(gray/red–gray/red)
3 Defective cylinder-#2 left ignition coil.Execute the diagnostic mode. 
(Code No.31)
Test the primary and secondary 
coils for continuity.
Replace if defective.
Refer to “CHECKING THE 
IGNITION COILS” on page 
7-99. 
						

							FUEL INJECTION SYSTEM
7-53
Fault  code  No. 35 Symptom Malfunction detected in the primary wire of the cylinder-#1 
left or right ignition coil.
Diagnostic code No. 30, 32 Cylinder-#1 left or right ignition coil
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Connections
Cylinder-#1 left or right ignition coil 
connector (primary coil side)
Main wire harness ECU coupler
Sub-wire harness 1 couplerCheck the connector and 
coupler for any pins that may be 
pulled out.
Check the locking condition of 
the connector and coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.Starting the 
engine and 
operating it at 
idle.
2 Open or short circuit in wire harness 
and/or sub lead.Repair or replace if there is an 
open or short circuit.
Between cylinder-#1 left or right 
ignition coil connector and ECU 
coupler/main wire harness.
(black/red–blue/red)
(orange–orange)
3 Defective cylinder-#1 left or right 
ignition coil.Execute the diagnostic mode. 
(Code No.30 or 32)
Test the primary and secondary 
coils for continuity.
Replace if defective.
Refer to “CHECKING THE 
IGNITION COILS” on page 
7-99. 
						

							FUEL INJECTION SYSTEM
7-54
Fault  code  No. 36 Symptom Malfunction detected in the primary wire of the cylinder-#2 
right ignition coil.
Diagnostic code No. 33 Cylinder-#2 right ignition coil
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 Connections
Cylinder-#2 right ignition coil 
connector (primary coil side)
Main wire harness ECU couplerCheck the connector and 
coupler for any pins that may be 
pulled out.
Check the locking condition of 
the connector and coupler.
If there is a malfunction, repair it 
and connect the coupler 
securely.Starting the 
engine and 
operating it at 
idle.
2 Open or short circuit in wire harness.Repair or replace if there is an 
open or short circuit.
Between cylinder-#2 right 
ignition coil connector and ECU 
coupler/main wire harness.
(black/red–blue/red)
(gray/black–gray/black)
3 Defective cylinder-#2 right ignition 
coil.Execute the diagnostic mode. 
(Code No.33)
Test the primary and secondary 
coils for continuity.
Replace if defective.
Refer to “CHECKING THE 
IGNITION COILS” on page 
7-99. 
						

							FUEL INJECTION SYSTEM
7-55
Fault code No. 37 Symptom Engine speed is high when the engine is idling.
Diagnostic code No. 54 ISC valve
Order Item/components and probable 
causeCheck or maintenance job Reinstatement 
method
1 ECU fuse is blown.Check the ECU fuse.
Refer to “CHECKING THE 
FUSES” on page 7-93.ISC valve 
returns to its 
original position 
by turning the 
main switch to 
“ON” and back 
to “OFF”.
Reinstated if 
the engine idle 
speed is within 
specification 
after starting 
the engine. 2 Throttle valve does not fully close.Check the throttle body.
Refer to “THROTTLE BODIES” 
on page 6-4.
Check the throttle cables.
Refer to “ADJUSTING THE 
THROTTLE CABLE FREE 
PLAY” on page 3-7.
3 ISC valve is stuck fully open due to 
disconnected ISC unit hose or 
coupler. (High engine idle speed is 
detected with the ISC valve stuck fully 
open even though signals for the valve 
to close are continuously being 
transmitted by the ECU.)Check that the ISC unit hose is 
not disconnected.
Check that the ISC unit coupler 
is not disconnected.
The ISC valve is stuck fully 
open if it does not operate when 
the main switch is turned “OFF”.
(Touch the ISC unit with your 
hand and check if it is vibrating 
to confirm if the ISC valve is 
operating.)
4 ISC valve is not moving correctly.Execute the diagnostic mode. 
(Code No.54)
After the ISC valve is fully 
closed, it opens to the standby 
opening position when the 
engine is started. This 
operation takes approximately 
12 seconds. Start the engine. If 
the error recurs, replace the 
throttle body assembly.