39
EFI SYSTEM
62 690 05 Rev. E
KohlerEngines.com
Removal Inspection
NOTE: Apply anti-seize compound only to threads.
Anti-seize compound will aff ect sensor performance if it gets
into lower shield of sensor.
1. If sensor has heavy deposits on lower shield, engine, oil, or fuel may be source.
2. If heavy carbon deposits are observed, incorrect engine fuel control may be occurring.
3. With sensor at room temperature measure heater circuit resistance, purple wire (Pin A) and white wire (Pin B),
resistance should be 8.1-11.1 Ω.
4. If a damaged sensor is found, identify root cause, which may be elsewhere in application. Refer to
Troubleshooting-Oxygen (O2) Sensor table.
5. A special "dry to touch" anti-seize compound is applied to all new oxygen sensors at factory. If recommended
mounting thread sizes are used, this material provides excellent anti-seize capabilities and no additional anti-seize
is needed. If sensor is removed from engine and reinstalled, anti-seize compound should be reapplied. Use an
oxygen sensor safe type anti-seize compound. It should be applied according to directions on label. Torque
sensor to 50.1 N·m (37 ft. lb.).
Troubleshooting-Oxygen (O2) Sensor
Condition
Possible Cause
Conclusion
Continuous low voltage output (less
than 400mV) observed with throttle
openings of 30-40% or more.
Fault codes P0131, P0171, or P0174
may set.
Shorted sensor or sensor circuit.
Shorted lead wire.
Wiring shorted to ground.
Replace sensor or replace and
properly route wiring.
Upstream or downstream exhaust
leaks observed.
Air leak at sensor.
Repair all exhaust leaks and torque
sensor to 50.1 N·m (37 ft. lb.).
Restricted fuel supply.
Resolve fuel supply issues from tank
to engine. Test fuel pressure. Perform
repairs necessary.
Misfi re
A misfi re causing incomplete
combustion will result in lean (low
voltage) values.
Sensor failure-stuck lean.
Replace sensor.
Continuous high voltage output
(600mV or more) observed with
throttle openings of 20% or less.
Fault codes P0172 or P0132 may set.
Silica poisoning.
Replace sensor. Identify and resolve
root cause.
Contaminated gasoline.
Purge fuel system and retest.
Wiring shorted to voltage.
Replace damaged harness.
Overly rich condition due to
unmetered fuel entering combustion
chamber.
Test fuel pressure. Inspect fuel pump
vent and evaporative emissions
hoses for raw fuel fl ow.
Inspect engine oil for fuel
contamination; drain and refi ll if
suspect.
Perform repairs as necessary.
Cold engine. Engine temperature
below 150°F (66°C) as displayed by
diagnostic software.
Normal operation, or engine operated
in an excessively cold environment.
Sensor failure-stuck rich.
Replace sensor.
No activity from sensor.
Diagnostic software displays
1.015 Volts continuously.
Fault codes P0031 or P0032 may set.
Heater circuit open or shorted.
Replace sensor.
Engine keyed ON with sensor
disconnected.
Historic codes.
Secure and/or confi rm sensor
connection and clear codes.
Contaminated gasoline.
Purge fuel system and retest.
Broken wire.
Damaged sensor.
Replace sensor.
