Honda BF135A - Page 244

BF135A•BF150A
5-91
Is there the battery voltage?
YES – Go to the step 6.
NO – Blown No.1 (30A) fuse, or repair open in the
wire between the A/F relay and the No.1
(10A) fuse.
-6. Turn the ignition switch ON. Measure the voltage
between the No.2 (Yellow/Red) terminal of the A/F
relay harness side 4P connector and the engine
ground.
Is there the battery voltage?
YES – Perform "3. A/F relay drive line check".
NO – Blown No.5 (10A) fuse, or repair open in the
wire between the A/F relay and the No.5 fuse.
3. A/F relay drive line check
-1. Turn the ignition switch OFF and connect the A/F relay
connector.
-2. Disconnect the ECM connector A.
-3. Turn the ignition switch ON and measure the voltage
between the test harness A-25 and the engine ground.
Is there the battery voltage?
YES – Substitute a known-good ECM and recheck.
NO – Repair open in the A/F relay and the ECM.
4. A/F heater check
-1. Turn the ignition witch OFF and disconnect the A/F
sensor 4P connector.
-2. Measure the resistance between the No.3 (Black) and
No.4 (Black) terminals of the A/F sensor’s sensor side
4P connector.
Is the resistance 2 – 3
?
YES – Perform “5. Heater line short circuit check”.
NO – Replace the A/F sensor.
5. Heater line short circuit check
-1. Turn the ignition switch OFF and disconnect the ECM
connector C.
-2. Check for the continuity between the test harness C-3
terminal and the engine ground, and between the C-4
terminal and the engine ground.
Is there the continuity?
YES – Repair short in the wire between the A/F sen-
sor and the ECM.
NO – Perform “6. Heater line open circuit check”.
C-4
C-3
A/F RELAY HARNESS SIDE
4P CONNECTOR
VIEWED FROM THE TERMINAL SIDE
A/F SENSOR SIDE
4P CONNECTOR
VIEWED FROM THE TERMINAL SIDE
A-25
IGP
(YELLOW/RED)
AFHT (BLACK) AFHT+ (BLACK)