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BF135A•BF150A
5-46
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.
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) and the No. 4 (White) terminals of the
ECM connector C.
Is the resistance 2 – 3
(at room temperature)?
YES –
Replace the A/F sensor and recheck. If it is
still abnormal, substitute a known-good ECM
and recheck.
NO –
Repair open in the wire between the A/F sen-
sor and the ECM.
DTC 41-4: A/F sensor heater is abnormal
1. Symptom reproduction test
-1. Connect the HDS pocket tester and clear the DTC
once. If the DTC can not be cleared, go on the trou-
bleshooting.
-2. Start the engine and warm it up for 5 minutes or more
by running the engine at 3,000 min
-1
(rpm) under no
load.
-3. Check the DTC again using the HDS pocket tester.
Does the DTC 41-4 appear?
YES –
Perform “2. A/F heater relay check”.
NO –
Temporary failure (Disappeared)
2. A/F heater relay check
-1. Turn the ignition switch OFF and disconnect the A/F
sensor 4P connector.
-2. Turn the ignition switch ON. Measure the voltage
between the No. 3 (White) terminal of the A/F sensor
harness side 4P connector and the engine ground.
Is there the battery voltage?
YES –
Perform “3. A/F heater harness check”.
NO –
Go to the step 3.
-3. Turn the ignition switch OFF and disconnect the A/F
heater relay 4P connector.
-4. Measure the voltage between the No. 1 (White/ Green)
terminal of the A/F heater relay harness side 4P con-
nector and the engine ground.
• Note that the battery voltage is constantly applied
to the White/Green terminal. Take care not to
short-circuit the terminal.
VIEWED FROM THE
TERMINAL SIDE
A/F SENSOR HARNESS
SIDE 4P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
AFHT+
(WHITE)
A/F HEATER RELAY HARNESS
SIDE 4P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
+B (WHITE/GREEN)
ECM CONNECTOR C
ECM CONNECTOR C
AFHT
(BLACK/WHITE)
AFHT+ (WHITE)
AFHT
(BLACK/WHITE)
AFHT+ (WHITE)
VIEWED FROM THE
TERMINAL SIDE