Kohler ECV940 Service Manual page 39

Visual Inspection
Sensor Wire Detail
A
Keep a minimum of 25 mm (1.0 in.) radius at
A
grommet.
NOTE: Always route harness away from hot exhaust
and away from moving parts.
NOTE: Do not attempt to clean sensor. Replace as
needed.
1. Look for a damaged or disconnected sensor-to-
engine harness connection.
2. Look for damage to sensor lead wire or associated
engine wiring due to cutting, chaffi ng or melting on a
hot surface.
3. Disconnect sensor connector and look for corrosion
in connector.
4. Try reconnecting sensor and observe if problem has
cleared.
5. Correct any problems found during visual check.
6. Inspect for any exhaust system leaks upstream or
downstream of oxygen sensor. Confi rm oxygen
sensor is secured to 50.1 N·m (37 ft. lb.).
All leaks must be repaired and an ECU reset must
be performed before proceeding with sensor testing.
7. Using KDS tool, document any trouble codes.
Determine if historic trouble codes are logically
related to current fault experienced. If uncertain,
clear codes and retest.
Sensor Signal Observation
Engine Harness O2 Sensor Connector Plug Detail
A
B C
A Red w/Black Stripe
C Purple
62 690 05 Rev. H
EFI SYSTEM-ELECTRONIC THROTTLE BODY (ETB)
D
B Dark Green
D Black
KohlerEngines.com
NOTE: Do not cut into or pierce sensor or engine
wiring to make this connection. Sensor
produces a very small signal. Corrosion or
damage to wiring could lead to an incorrect
signal because of repairs or contamination to
sensor.
1. With sensor connected and using KOHLER
Diagnostic System (KDS) Gen 2, see Tools and
Aids, start engine to observe O2 sensor activity. Run
engine at suffi cient speed to bring sensor and
engine up to operating temperature (engine
temperature of 150°F (66°C) or more displayed by
KDS tool).
Maintained throttle openings of less than 20%
typically display closed loop operation where sensor
output voltage should cycle between 0.05 to 0.95
Volts.
Maintained throttle openings of 30-40% and above
typically display open loop operation where sensor
should have above 0.500 Volt. Occasional spikes
outside these values is normal. Lack of continuous
fl uctuation is not an indication of a defective sensor.
2. With key ON and engine OFF, sensor connected,
using diagnostic software, O2 volts displayed should
be more than 1.0 volt. This voltage is generated by
ECU. If not present, there may be a power and/or
ground supply fault to engine harness or ECU, a
fault of engine harness itself (refer to Visual
Inspection), or a fault of ECU.
It is advisable to use an electronic meter such as a
digital voltmeter. Simple mechanical meters may
place a heavy electrical load on sensor and cause
inaccurate readings. Since resistance of sensor is
highest at low temperatures, such meters will cause
largest inaccuracies when sensor is in a cool
exhaust.
With key ON and sensor unplugged, using a digital
voltmeter, observe voltage between Pin socket C
and Pin socket D of engine wiring harness (refer to
engine harness connector plug detail at top of page).
Voltage should read approximately 5.0 volts.
3. Using a digital voltmeter, observe system sensor
voltage between Pin socket A and negative (-)
battery ground. Battery voltage should be seen. If
battery voltage is not seen, inspect engine wiring,
fuses, and/or electrical connections.
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