Kohler Command PRO CH749, Service Manual

Page: 46 / 154

5.14
Section 5
EFI Fuel System
Visual Inspection
1. Look for a damaged or disconnected sensor-to-
engine harness connection.
2. Look for damage to the sensor lead wire or the
associated engine wiring due to cu tt ing, cha ffi ng
or melting on a hot surface.
3. Disconnect the sensor connector and look for
corrosion in the connector.
4. Try reconnecting the sensor and observe if the
problem has cleared.
5. Correct any problems found during the visual
check.
Sensor Signal Observation
If the visual examination shows no problems, connect
the sensor back to the engine harness.
NOTE: Do not cut into or pierce the sensor or engine
wiring to make this connection. The sensor
produces a very small signal. Corrosion
or damage to the wiring could lead to
an incorrect signal because of repairs or
contamination to the sensor.
1. Using a voltmeter or diagnostic so ft ware observe
the voltage before the engine is started. With the
key ON, the voltage should read about 1.0 volt.
This voltage is generated by the ECU. If it is not
present, disconnect the sensor and observe the
voltage at the harness connector. If the voltage is
now present, there is a short in the sensor or
associated wiring and corrective action should be
taken. If the voltage still is not present, there is a
problem with the ECU or engine harness.
2. Reconnect the sensor and start the engine. Run
the engine at su ffi cient speed to bring the sensor
up to operating temperature. Maintain for 1 to 2
minutes to ensure that the engine has gone closed
loop. Once in closed loop, the sensor voltage
should cycle between about 100 to 250 mv and
700 to 900 mv. If this cycling is not observed, a
determination must be made. If the problem is
with the engine or the sensor.
3. Check engine harness for ba tt ery voltage on the
heater circuit.
NOTE: Using the diagnostic so ft ware, the wiring and
ECU integrity can be checked by grounding
the signal wire; the output of the sensor, read
on the so
ft ware, should be around 4 mv.
Removal Inspection
1. If the sensor has heavy deposits on the lower
shield, the engine, oil, or fuel may be the source.
2. If heavy carbon deposits are observed, incorrect
engine fuel control may be occurring.
3. If the sensor is at room temperature, measure
between the signal leads, the black wire (Pin C)
and grey wire (Pin D) a
tt ached to the sensor (see
Figure 5-9). If the resistance is less than one
megohm, the sensor has an internal short.
4. With the sensor at room temperature measure the
heater circuit resistance, purple wire (Pin A) and
white wire (Pin B), resistance should be
8.1-11.1
Ω .
5. If a damaged sensor is found, identify the root
cause, which may be elsewhere in the application.
The table on the following page summarizes
sensor symptoms and corrections. It includes
items, which apply to both diagnostics and
application system design.
6. A special "dry to touch" anti-seize compound is
applied to all new oxygen sensors at the factory.
If the recommended mounting thread sizes are
used, this material provides excellent anti-seize
capabilities and no additional anti-seize is
needed. If the sensor is removed from the engine
and reinstalled, the anti-seize compound should
be reapplied. Use a oxygen sensor safe type
anti-seize compound. It should be applied
according to the directions on the label.
NOTE: Apply the anti-seize compound only to the
threads. Anti-seize compound will a ff ect
sensor performance if it gets into the lower
shield of the sensor.