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BF135A•BF150A
5-47
Is there the battery voltage?
YES –
Go to the step 5.
NO –
Blown No. 1 fuse, or repair open in the wire
between the A/F heater relay and the No. 1
fuse.
-5. Turn the ignition switch ON. Measure the voltage
between the No. 3 (White) terminal of the A/F heater
relay harness side 4P connector and the engine
ground.
Is there the battery voltage?
YES –
NO –
Repair open in the wire between the A/F
heater relay and the No. 5 fuse.
-6. Check the A/F heater relay (single unit check) (P. 18-
Is the A/F heater relay normal?
YES –
NO –
Replace the A/F heater relay.
-7. Turn the ignition switch OFF and disconnect the ECM
connector A.
-8. Check for continuity between the No. 4 (Green/
Orange) terminal of the A/F heater relay harness side
4P connector and the No. 25 (Green/Orange) terminal
of the ECM connector A.
Is there the continuity?
YES –
NO –
Repair open in the wire between the A/F
heater relay and the ECM.
-9. Check for the continuity between the No. 3 (White) ter-
minal of the A/F heater relay harness side 4P connec-
tor and the No. 3 (White) terminal of the A/F sensor
harness side 4P connector.
Is there the continuity?
YES –
Perform “3. A/F heater check”.
NO –
Repair open in the wire between the A/F
heater relay and the A/F sensor.
3. A/F heater check
-1. Turn the ignition switch OFF and disconnect the A/F
sensor 4P connector.
-2. Measure the resistance between the No. 3 (Black) and
the No. 4 (Black) terminals of the A/F sensor side 4P
connector.
Is the measured resistance 2 – 3
(at room tem-
perature)?
YES –
Perform “4. Heater line short circuit check”.
NO –
Replace the A/F sensor.
A/F HEATER RELAY HARNESS
SIDE 4P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
AFHT+ (WHITE)
A/F HEATER RELAY
HARNESS SIDE
4P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
AFHT-
(GREEN/ORANGE)
ECM CONNECTOR A
A/F SENSOR
HARNESS SIDE
4P CONNECTOR
A/F HEATER RELAY
HARNESS SIDE
4P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
AFHT+
(WHITE)
AFHT+
(WHITE)
A/F SENSOR SIDE
4P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
AFHT (BLACK)
AFHT+ (BLACK)