Oxygen Sensor Removal/Installation
Refer to the Oxygen Sensor Removal/Installation (Equipped Models) in the Electrical System chapter.
Oxygen Sensor Inspection

Main Harness [B] Oxygen Sensor [C]
Special Tool - Measuring Adapter: 57001-1700

Oxygen Sensor Output Voltage Connections to Adapter: Digital Meter (+) → R (sensor BK) lead Digital Meter (–) → BK (sensor GY) lead

Do not disconnect the air switching valve connector [B].

Air Cleaner Housing (see Air Cleaner Housing Installation in the Fuel System (DFI) chapter) Fuel Tank (see Fuel Tank Installation in the Fuel System (DFI) chapter)

Measuring Adapter [A]
Output Voltage (with Plugs, Rich) Standard: DC 0.8 V or more

| WARNING The engine gets extremely hot during normal operation and can cause serious burns. Never touch a hot engine. |

Air Cleaner Housing (see Air Cleaner Housing Installation in the Fuel System (DFI) chapter) Fuel Tank (see Fuel Tank Installation in the Fuel System (DFI) chapter)
Output Voltage (without Plugs, Lean) Standard: DC 0.24 V or less
If the reading is out of the standard (with plugs: 0.8 V or more, without plugs: 0.24 V or less), remove the ECU and check the wiring for continuity between harness connectors.
Special Tool - Hand Tester: 57001-1394

Disconnect the ECU and sensor connectors.
Wiring Continuity Inspection ECU Connector [A] ←→ Oxygen Sensor Connector [B] W/BL lead (ECU terminal 35) [C] BR/BK lead (ECU terminal 13) [D]
If the wiring is good, replace the sensor.
If the reading is within the standard (with plugs: 0.8 V or more, without plugs: 0.24 V or less), check the ECU for its ground and power supply (see ECU Power Supply Inspection in the Fuel System (DFI) chapter).
If the ground and power supply are good, replace the ECU (see ECU Removal/Installation in the Fuel System (DFI) chapter).
Oxygen Sensor Circuit

1. ECU
2. Oxygen Sensor
3. Ignition Switch
4. Joint Connector F
5. Joint Connector A
6. Fuse Box 1
7. Ignition Fuse 15 A
8. Relay Box
9. ECU Main Relay
10. Frame Ground 3
11. Starter Relay
12. ECU Fuse 15 A
13. Main Fuse 30 A
14. Battery
15. Engine Ground
Subthrottle Sensor Resistance Inspection
Exhaust Butterfly Valve Actuator Sensor (Service Code 34)Subthrottle Valve Actuator Inspection
NOTE
Be sure the battery is fully charged.
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter).
Turn the ignition switch to ON.
Check to see that all the subthrottle valves [A] open and
close smoothly.
Turn the ignition switch to OFF.
I ...
Radiator Inspection
Remove the radiator (see Radiator and Radiator Fan Removal).
Check the radiator core.
If there are obstructions to air flow, remove them.
If the corrugated fins [A] are deformed, carefully
straighten them.
If the air passages of the radiator core are blocked more
than 20% by unremovable ...
Tachometer
The tachometer shows the engine
speed in revolutions per minute (r/min,
rpm).
On the right side of the tachometer
face is a portion called the “red zone”.
Engine r/min (rpm) in the red zone is
above maximum recommended engine
speed and is also above the range for
good performance.
...