Honda BF135A Manual page 201

BF135A•BF150A
4. Heater line short circuit check
-1. Turn the ignition switch OFF and disconnect the ECM
connector C.
-2. Check for the continuity between the No. 3
(Black/White) terminal of the ECM connector C and
the engine ground, and between the No. 4 (White) ter-
minal of the ECM connector C and the engine ground.
ECM CONNECTOR C
AFHT
(BLACK/WHITE)
VIEWED FROM THE
TERMINAL SIDE
Is there the continuity?
YES – Repair short in the wire between the A/F sen-
sor and the ECM.
NO – Perform "5. Heater line open circuit check".
5. Heater line open circuit check
-1. Turn the ignition switch OFF and connect the A/F sen-
sor 4P connector.
-2. Measure the resistance between the No. 3 (Black/
White) terminal and the No. 4 (White) terminal of the
ECM connector C.
ECM CONNECTOR C
AFHT
(BLACK/WHITE)
VIEWED FROM THE
TERMINAL SIDE
Is the resistance 2 – 3
YES – Perform "6. Sensor line short circuit check".
NO – Repair open in the wire between the A/F sen-
sor and the ECM.
6. Sensor line short circuit check
-1. Disconnect the ECM connector B.
-2. Disconnect the A/F sensor 4P connector.
AFHT+
(WHITE)
AFHT+ (WHITE)
(at room temperature)?
-3. Check for the continuity between the No. 3 (Black/
White) terminal of the ECM connector C and the
respective terminals of the No. 1 (White/Black) and the
No. 2 (Black/Yellow) terminals of the A/F sensor har-
ness side 4P connector.
A/F SENSOR
HARNESS SIDE
4P CONNECTOR
AFV1
(WHITE/
BLACK)
VIEWED FROM THE
TERMINAL SIDE
Is there the continuity?
YES – Repair short in the wire between the A/F sen-
sor and the ECM.
NO – Go to the step 4.
-4. Check for continuity between the No. 4 (White) termi-
nal of the ECM connector C and the respective termi-
nals of the No. 1 (White/Black) and the No. 2
(Black/Yellow) terminals of the A/F sensor harness
side 4P connector.
ECM CONNECTOR C
AFHT+
(WHITE)
VIEWED FROM THE
TERMINAL SIDE
Is there the continuity?
YES – Repair short in the wire between the A/F sen-
sor and the ECM.
NO – Replace the A/F sensor and recheck. If it is
still abnormal, substitute a known-good ECM
and recheck.
ECM CONNECTOR C
AFC1
(BLACK/
AFHT
YELLOW)
(BLACK/ WHITE)
A/F SENSOR
HARNESS SIDE
4P CONNECTOR
AFC1
(BLACK/
AFV1
YELLOW)
(WHITE/
BLACK)
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