38
EFI System
KohlerEngines.com
66 690 14 Rev. A
Troubleshooting-Oxygen Sensor (O
2
)
Condition
Possible Cause
Conclusion
Low voltage output.
Shorted sensor or sensor circuit.
Shorted lead wire.
Wiring shorted to ground.
Replace sensor or repair wiring.
Contamination of air reference.
Remove source of external
contamination, protect air reference
area.
Air leak at sensor or gasket, sensor
upper shield damage.
Use recommended torque at
installation, replace gasket or sensor.
Revise application exhaust.
Shield sensor from damage.
High voltage output.
Silica poisoning.
Replace sensor.
Contaminated gasoline.
Use high quality fuel.
Engine problem; mis
fi
re.
Correct cause of mis
fi
re.
Excessive rich air/fuel ratio.
Check for high fuel pressure
Leaking injector
Liquid fuel in vent line
Wiring shorted to voltage.
Repair wiring.
Open circuit, no activity from sensor.
Broken element.
Sensor dropped.
Hard blow to engine or exhaust
system.
Defective sensor.
Thermal shock.
Replace sensor.
Slow time response.
Open heater circuit.
Improper handling.
Carbon deposits.
Replace sensor.
Improper fueling.
Correct fueling.
Incorrect or contaminated fuel.
Use high quality fuel.
Excessive engine oil consumption
causing exhaust contamination or
other exhaust side contamination.
Correct engine condition.
Heater circuit open/shorted or out of
speci
fi
cation.
Repair short in harness wires, replace
sensor.
