Inspection Procedure 4: The Headlamp(s) do not
Illuminate.
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Whenever the ECU is replaced, ensure that
the input and output signal circuits are normal.
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COMMENTS ON TROUBLE SYMPTOM
If any of the headlamps does not
illuminate, the wiring harness connector(s), the bulb or the fuse may be
defective or burned out.
PROBABLE CAUSES
- Malfunction of the headlamp bulbs
- Damaged harness wires and connectors
DIAGNOSIS PROCEDURE
STEP 1. Connector check: A-40 headlamp (HI: RH)
connector or A-23 headlamp (HI: LH) connector, A-41 headlamp (LO:
RH) connector <without discharge headlamp>, A-20 headlamp
(LO: LH) connector <without discharge headlamp>, A-39
headlamp (LO: RH) connector <with discharge headlamp> or
A-25 headlamp (LO: LH) connector <with discharge
headlamp>.
Q.
Is the check result normal?
Go to Step
2.
Repair the defective
connector.
STEP 2. Check the bulbs of the
headlamp.
Check the bulb of the lamp which does not
illuminate.
Q.
Is the check result normal?
Go to Step
3.
Replace the bulb of
the lamp which does not illuminate.
STEP 3.
Resistance measurement at the A-40 headlamp (HI: RH) connector or
A-23 headlamp (HI: LH) connector, A-41 headlamp (LO: RH) connector
<without discharge headlamp>, A-20 headlamp (LO: LH)
connector <without discharge headlamp>, A-39 headlamp (LO:
RH) connector <with discharge headlamp> or A-25 headlamp
(LO: LH) connector <with discharge
headlamp>.
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(1)Disconnect the connector, and measure at the
wiring harness side.
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(2)Check the resistance between the lamp connector
and body earth.
- Resistance between A-40 headlamp (HI: RH) connector
terminal No.1 and body earth
- Resistance between A-23 headlamp (HI: LH) connector
terminal No.1 and body earth
- Resistance between A-41 headlamp (LO: RH) connector
terminal No.1 and body earth <without discharge
headlamp>
- Resistance between A-20 headlamp (LO: LH) connector
terminal No.1 and body earth <without discharge
headlamp>
- Resistance between A-39 headlamp (LO: RH) connector
terminal No.1 and body earth <with discharge
headlamp>
- Resistance between A-25 headlamp (LO: LH) connector
terminal No.1 and body earth <with discharge
headlamp>
OK: Continuity exists (2 Ω or
less)
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Q.
Is the check result normal?
Go to Step 5.
Go to Step
4.
STEP 4. Check the wiring harness from
A-40 headlamp (HI: RH) connector terminal No.1 or A-23 headlamp (HI:
LH) connector terminal No.1, A-41 headlamp (LO: RH) connector
terminal No.1 <without discharge headlamp> or A-20 headlamp
(LO: LH) connector terminal No.1 <without discharge
headlamp>, A-39 headlamp (LO: RH) connector terminal No.1
<with discharge headlamp> or A-25 headlamp (LO: LH)
connector terminal No.1 <with discharge headlamp> to body
earth.
- Check the earth wires for open circuit.
Q.
Is the check result normal?
Go to Step
7.
Repair the wiring
harness.
STEP 5. Connector check: A-08X
front-ECU connector.
Q.
Is the check result normal?
Go to Step
6.
Repair the defective
connector.
STEP 6. Check the wiring harness
from A-40 headlamp (HI: RH) connector terminal No.2, A-23 headlamp
(HI: LH) connector terminal No.2, A-41 headlamp (LO: RH) connector
terminal No.2 <without discharge headlamp> or A-20 headlamp
(LO: LH) connector terminal No.2 <without discharge
headlamp>, A-39 headlamp (LO: RH) connector terminal No.2
<with discharge headlamp> or A-25 headlamp (LO: LH)
connector terminal No.2 <with discharge headlamp> to A-08X
front-ECU connector terminal Nos.2 (HI) or 6
(LO).
- Check the output lines for open circuit.
Q.
Is the check result normal?
Go to Step
7.
Repair the wiring
harness.
STEP 7. Retest the
system.
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(1)Replace the socket of the defective
headlamp.
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(2)Check that the headlamps operate
normally.
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Q.
Is the check result normal?
The trouble can be an
intermittent malfunction (Refer to GROUP 00 - How to Cope with
Intermittent Malfunction 
).
Replace the headlamp
assembly.