Kohler Command CV730 User Manual download pdf (Page 78)

5B.11

Section 5B

EFI Fuel System

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

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,

752°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. Look for a voltage reading from

0.2 v-1.0 v.

a. If voltage is in the specified range, go to Step

b. If 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 good

ground location. Start and run the engine at

3/4 throttle and note the voltage reading being

signaled by the oxygen sensor. The reading

should cycle between 0.2 v and 1.0 v, which

indicates the oxygen sensor is functioning

normally and fuel delivery is within

prescribed parameters. If the voltage readings

show a steady decline, rev the engine and

check the indicated reading again. If the

voltage momentarily increases and then again

declines, without cycling, the 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 voltage

from 0.2 to 1.0 v 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

andthe 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 the sensor still hot (minimum of 400°C,

752°F), switch the meter to the Rx1K or Rx2K

scale and check the resistance between the sensor

lead and the sensor case. It should be less than

2.0 K

ΩΩ

Ω.

a. If the resistance is less than 2.0 K

ΩΩ

Ω go to

Step 4.

b. If the resistance is greater than 2.0 K

ΩΩ

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 sensor cool, the resistance

should be greater than 1.0 M

ΩΩ

Ω.

a. If the resistance is greater than 1.0 M

ΩΩ

Ω go to

Step 5.

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Kohler Command CV730 User Manual Page 78

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