Kohler Aegis LH685, Руководство по обслуживанию

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5B.10
Section 5B
EFI Fuel System
If voltage momentarily increases and then again
declines, without cycling, engine may be
running lean due to incorrect TPS initialization.
Shut off the engine, perform TPS initialization,
and then repeat the test. If TPS initialization
cannot be achieved, perform step c.
c. Replace the oxygen sensor (see next page).
Run the engine long enough to bring the new
sensor up to temperature and repeat the
output test from step 1. The cycling oltage
from 0.2 to 1.0 volt should be indicated.
2. Move the black voltmeter lead to the engine
ground location and repeat the output test. The
same voltage (0.2 v-1.0 v) should be indicated.
a. If the same voltage reading exists, go on to
step 3.
b. If the voltage output is no longer correct, a bad
ground path exists between the sensor and
the engine ground. Touch the black lead at
various points, backtracking from the engine
ground back toward the sensor, watching for a
voltage change at each location. If the correct
voltage reading reappears at some point,
check for a problem (rust, corrosion, loose
joint or connection) between that point and the
previous checkpoint. For example, if the
reading is too low at points on the crankcase,
but correct voltage is indicated when the black
lead is touched to the skin of the muffler, the
flange joints at the exhaust ports become
suspect.
3. With sensor still hot (minimum of 400°C, 752°F),
switch meter to the Rx1K or Rx2K scale and
check the resistance between the sensor lead and
sensor case. It should be less than 2.0 K
Ω Ω Ω Ω Ω
.
a. If the resistance is less than 2.0 K
Ω Ω Ω Ω Ω
, go to
step 4.
b. If the resistance is greater than 2.0 K
Ω Ω Ω Ω Ω
, the
oxygen sensor is bad, replace it.
4. Allow the sensor to cool (less than 60°C, 140°F)
and retest the resistance with the meter set on the
Rx1M scale. With the sensor cool, the resistance
should be greater than 1.0 M
Ω Ω Ω Ω Ω
.
a. If the resistance is greater than 1.0 M
Ω Ω Ω Ω Ω
, go to
step 5.
The oxygen sensor can function only after being heated
by exhaust temperatures to a minimum of 375°C
(709°F). A cold oxygen sensor will require
approximately 1-2 minutes at moderate engine load to
warm sufficiently to generate a voltage signal. Proper
grounding is also critical. The oxygen sensor grounds
through the metal shell, so a good, solid, unbroken
ground path back through the exhaust system
components, engine, and wiring harness is required.
Any disruption or break in the ground circuit can affect
the output signal and trigger misleading fault codes.
Keep that in mind when doing any troubleshooting
associated with the oxygen sensor. The oxygen sensor
can also be contaminated by leaded fuel, certain RTV
and/or other silicone compounds, carburetor cleaners,
etc. Use only those products indicated as “O
2
Sensor
Safe.”
Service
Like the other sensors already discussed, the oxygen
sensor is a non-serviceable component. Complete
replacement is required if it is faulty. The sensor and
wiring harness can be checked as follows.
NOTE: All tests should be conducted with a good
quality, high-impedance, digital VOA meter for
accurate results.
1. Oxygen sensor must be hot (minimum of 400°C,
725°F). Run engine for about 5 minutes. With the
engine running, disconnect the oxygen sensor lead
from the wiring harness. Set VOA meter for DC
volts and connect the red lead to the disconnected
sensor lead, and the black lead to the sensor
shell. Check for a cycling voltage reading between
0.2 and 1.0 volt.
a. If voltage is in the specified range, go to step 2.
b. If the voltage is not in the specified range,
reconnect the oxygen sensor lead. With the
lead connected, probe or connect the sensor
connection with the red VOA meter lead.
Attach the black VOA meter lead to a known
good ground location. Start and run the engine
at 3/4 throttle and note the voltage output.
The reading should cycle between 0.2 and 1.0
volt, which indicates the oxygen sensor is
functioning normally and also the fuel delivery
controlled by the ECU is within prescribed
parameters. If the voltage readings show a
steady decline, bump the governor lever to
make the engine accelerate very quickly and
check the reading again.
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