To Replace Oxygen Sensor - Kohler command pro ECH749 Service Manual

5. With oxygen sensor disconnected and engine not
running, disconnect main harness connector from
ECU and set meter to Rx1 scale. Check circuit
continuity as follows.
"24 Pin" (MSE 1.0) Plastic-Cased ECU:
Check for continuity from pin #15 of ECU
connector (see page ) to shell of oxygen
sensor, and from pin #11 to sensor connector
terminal of main harness. Both tests should
indicate continuity.
"32 Pin" (MSE 1.1) Plastic-Cased ECU:
Check for continuity from pin #19 of ECU
connector (see page) to shell of oxygen
sensor, and from pin #20 to sensor terminal of
main harness. Both tests should indicate
continuity.
a. If there is no continuity displayed in either of
tests, check harness circuit for breaks or damage,
and connections for poor contact, moisture, or
corrosion. If no continuity was found in fi rst test,
also check for a poor/broken ground path back
through exhaust system, engine, and mounting
(sensor is grounded through its shell).
b. If continuity is indicated, go to step 6.
6. With key switch in ON/RUN position, using a high
impedance voltmeter, check voltage from wiring
harness oxygen sensor connector to engine ground
location. Look for a steady voltage from 350-550 mv
(0.35-0.55 v).
a. If voltage reading is not as specifi ed, move black
voltmeter lead to negative post of battery, to be
certain of a good ground. If voltage is still not
correct, ECU is probably bad.
b. If voltage readings are correct, clear fault codes
and run engine to check if any fault codes
reappear.

To Replace Oxygen Sensor

1. Disconnect oxygen sensor connector from wiring
harness.
2. Loosen and remove oxygen sensor from exhaust
manifold/muffl er assembly.
3. Apply anti-seize compound sparingly to threads of
new oxygen sensor, if none already exists. DO NOT
get any on tip as it will contaminate sensor. Install
sensor and torque to 50-60 N·m (37-44 ft. lb.).
4. Reconnect lead to wiring harness connector. Make
sure it can not contact hot surfaces, moving parts,
etc.
5. Test run engine.
A malfunctioning relay can result in starting or operating
diffi culties. Relay and related wiring can be tested as
follows:
1. Disconnect relay connector plug from relay.
2. Connect black lead of VOA meter to a chassis
ground location. Connect red lead to #86 terminal in
relay connector. Set meter to test resistance (Rx1).
Turn ignition switch from OFF to ON. Meter should
indicate continuity (ground circuit is completed) for 1
to 3 seconds. Turn key switch back off.
24 690 01 Rev. K
a. Clean connection and check wiring if circuit was
not completed.
3. Set meter for DC voltage. Touch red tester lead to
#30 terminal in relay connector. A reading of 12 volts
should be indicated at all times.
4. Connect red lead of meter to #85 terminal in relay
connector. Turn key switch to ON position. Battery
voltage should be present.
a. No voltage present indicates a problem with key
switch, in wiring, or at connector.
b. If voltage is present, wiring to connector is good.
Turn ignition switch 'OFF and proceed to Step 5
to test relay.
5. Connect an ohmmeter (Rx1 scale) between #85 and
#86 terminals in relay. There should be continuity.
6. Attach ohmmeter leads to #30 and #87 terminals in
relay. First, there should be no continuity. Using a 12
volt power supply, connect positive (+) lead to #85
terminal and touch negative (-) lead to #86 terminal.
When 12 volts is applied, relay should activate and
continuity should exist between #30 and #87
terminals. Repeat test several times. If, at any time
relay fails to activate circuit, replace relay.
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