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Home › Lexus › 2003 › IS 300 Base, Automatic › Repair and Diagnosis › Body & Frame › Windows › Troubleshooting (Body Electrical) › Problem Symptoms Table › Headlight And Taillight System

Headlight And Taillight System

This system uses the multiplex communication system, so check diagnosis system of the multiplex communication system before you proceed with troubleshooting.

HINT:

To inspect the bulb and light control ECU, replace them with the ones working normally and judge whether they work normally or not.

PROBLEM SYMPTOMS - HEADLIGHT AND TAILLIGHT SYSTEM (W/O DAYTIME)

Symptom Suspect Area Go To
"Automatic light control system" does not operate.
  1. Automatic Light Control Sensor
  2. Light Control Switch
  3. Door Courtesy Switch
  4. Wire Harness
  5. Theft Deterrent ECU
  6. Body ECU
  1. INSPECTION
  2. INSPECTION
  3. INSPECTION
  4. -
  5. SYSTEM OPERATION CHECK
  6. BODY CONTROL SYSTEM
Auto turn-off system does not operate when the driver's door is opened.
  1. Drivers Door Courtesy Switch
  2. Body ECU
  1. INSPECTION
  2. BODY CONTROL SYSTEM
Auto turn-off system: Headlight and taillight do not come on.
  1. Body ECU
  2. Wire Harness
  1. BODY CONTROL SYSTEM
  2. -
Auto turn-off system: Headlight and taillight stay on.
  1. Body ECU
  2. Wire Harness
  1. BODY CONTROL SYSTEM
  2. -
Only one headlight comes on.
  1. Bulb
  2. Light Control Sensor
  3. Wire Harness
  1. -
  2. INSPECTION
  3. -
"LO-Beam" does not light (All).
  1. Headlight Control Relay
  2. Light Control Sensor
  3. Wire Harness
  1. INSPECTION
  2. INSPECTION
  3. -
"LO-Beam" does not light (One side).
  1. Bulb
  2. H-LP L-LWR Fuse
  3. H-LP R-LWR Fuse
  4. Wire Harness
  1. -
  2. LOCATION
  3. LOCATION
  4. -
"Hl-Beam" does not light (All).
  1. Headlight Dimmer Switch
  2. Wire Harness
  1. INSPECTION
  2. -
"Hl-Beam" does not light (One side).
  1. Bulb
  2. H-LP L-UPR Fuse
  3. H-LP R-UPR Fuse
  4. Wire Harness
  1. -
  2. LOCATION
  3. LOCATION
  4. -
"Flash" does not light.
  1. H-LP L-UPR Fuse
  2. H-LP R-UPR Fuse
  3. Headlight Dimmer Switch
  4. Light Control ECU
  5. Wire Harness
  1. LOCATION
  2. LOCATION
  3. INSPECTION
  4. -
  5. -
"Flash" does not light.
  1. Bulb
  2. Light Control ECU
  3. Wire Harness
  1. -
  2. -
  3. -
Headlight does not come on.
  1. Headlight Control Relay
  2. Light Control Switch
  3. Light Control ECU
  4. Wire Harness
  1. INSPECTION
  2. INSPECTION
  3. -
  4. -
Headlight does not come on.
  1. Bulb
  2. Light Control ECU
  3. Wire Harness
  1. -
  2. -
  3. -
Headlight flickers.
  1. Bulb
  2. Light Control ECU
  3. Wire Harness
  1. -
  2. -
  3. -
Headlight is dark.
  1. Bulb
  2. Light Control ECU
  3. Wire Harness
  1. -
  2. -
  3. -
 
Only one taillight comes on.
  1. Bulb
  2. Wire Harness
  1. -
  2. -
Taillight does not come on. (Headlight is normal)
  1. TAIL Fuse
  2. GAUGE Fuse
  3. Taillight Control Relay
  4. Light Failure Relay
  5. Light Control Switch
  6. Wire Harness
  1. LOCATION
  2. LOCATION
  3. INSPECTION
  4. INSPECTION
  5. INSPECTION
  6. -
Taillight does not come on. (Headlight does not light)
  1. Light Control Switch
  2. Wire Harness
  1. INSPECTION
  2. -
Rear combination light does not come on.
  1. Light Failure Relay
  2. Wire Harness
  3. Bulb
  1. INSPECTION
  2. -
  3. -

w/ Daytime running light system: 



This system uses the multiplex communication system, so check diagnosis system of the multiplex communication system before you proceed with troubleshooting.

HINT:

To inspect the bulb and light control ECU, replace them with the ones working normally and judge whether they work normally or not.

PROBLEM SYMPTOMS - HEADLIGHT AND TAILLIGHT SYSTEM (WITH DAYTIME)

Symptom Suspect Area Go To
"Automatic light control system" does not operate.
  1. Automatic Light Control Sensor
  2. Light Control Switch
  3. Door Courtesy Switch
  4. Wire Harness
  5. Theft Deterrent ECU
  6. Body ECU
  1. INSPECTION
  2. INSPECTION
  3. INSPECTION
  4. -
  5. SYSTEM OPERATION CHECK
  6. BODY CONTROL SYSTEM
Auto turn-off system does not operate when the driver's door is opened.
  1. Drivers Door Courtesy Switch
  2. Body ECU
  1. INSPECTION
  2. BODY CONTROL SYSTEM
Auto turn-off system: Headlight and taillight do not come on.
  1. Body ECU
  2. Wire Harness
  1. BODY CONTROL SYSTEM
  2. -
Auto turn-off system: Headlight and taillight stay on.
  1. Body ECU
  2. Wire Harness
  1. BODY CONTROL SYSTEM
  2. -
Only one headlight comes on.
  1. Daytime Running Light No. 2 Relay
  2. Daytime Running Light Main Relay
  3. Bulb
  4. Light Control ECU
  5. Wire Harness
  6. Combination Meter
  1. INSPECTION
  2. INSPECTION
  3. -
  4. -
  5. -
  6. CIRCUIT TESTS
"LO-Beam" does not light (All).
  1. Headlight Control Relay
  2. Light Control ECU
  3. Wire Harness
  1. INSPECTION
  2. -
  3. -
"LO-Beam" does not light (One side).
  1. Bulb
  2. H-LP L-LWR Fuse
  3. H-LP R-LWR Fuse
  4. Light Control ECU
  5. Wire Harness
  1. -
  2. LOCATION
  3. LOCATION
  4. -
  5. -
"HI-Beam" does not light (All).
  1. Headlight Dimmer Switch
  2. Daytime Running Light Main Relay
  3. Wire Harness
  4. Combination Meter
  1. INSPECTION
  2. INSPECTION
  3. -
  4. CIRCUIT TESTS
"HI-Beam" does not light (One side).
  1. Bulb
  2. H-LP L-UPR Fuse
  3. H-LP R-UPR Fuse
  4. Daytime Running Light No. 2 Relay
  5. Wire Harness
  1. -
  2. LOCATION
  3. LOCATION
  4. LOCATION
  5. -
"Flash" does not light.
  1. Headlight Dimmer Switch
  2. Daytime Running Light Main Relay
  3. Wire Harness
  4. Combination Meter
  1. INSPECTION
  2. INSPECTION
  3. -
  4. CIRCUIT TESTS
Headlight does not come on.
  1. Headlight Control Relay
  2. Daytime Running Light Main Relay
  3. Daytime Running Light No.2 Relay
  4. Headlight Dimmer Switch
  5. Light Control Switch
  6. Wire Harness
  7. Light Control ECU
  8. Bulb
  9. Combination Meter
  1. INSPECTION
  2. INSPECTION
  3. INSPECTION
  4. INSPECTION
  5. INSPECTION
  6. -
  7. -
  8. -
  9. CIRCUIT TESTS
Headlight does not come on with light control switch in HEAD.
  1. Light Control Switch
  2. Light Control ECU
  3. Wire Harness
  1. INSPECTION
  2. -
  3. -
Headlight does not go out with light control switch in OFF.
  1. Headlight Control Relay
  2. Light Control ECU
  3. Wire Harness
  1. INSPECTION
  2. -
  3. -
Headlight flickers.
  1. Bulb
  2. Light Control ECU
  3. Wire Harness
  1. -
  2. -
  3. -
Headlight is dark.
  1. Bulb
  2. Light Control ECU
  3. Wire Harness
  1. -
  2. -
  3. -
Taillight does not come on with light control switch in TAIL.
  1. Taillight Control Relay
  2. Light Control Switch
  3. Wire Harness
  1. INSPECTION
  2. INSPECTION
  3. -
Taillight does not go out with light control switch in OFF.
  1. Taillight Control Relay
  2. Light Control Switch
  3. Wire Harness
  1. INSPECTION
  2. INSPECTION
  3. -
Headlight does not come on with engine running and light control switch in OFF.
  1. ECU-B Fuse
  2. GAUGE Fuse
  3. Daytime Running Light Main Relay
  4. Daytime Running Light No.2 Relay
  5. Generator L Terminal
  6. Parking Brake Switch
  7. Wire Harness
  8. Combination Meter
  1. LOCATION
  2. LOCATION
  3. INSPECTION
  4. INSPECTION
  5. CIRCUIT TESTS
  6. CIRCUIT TESTS
  7. -
  8. -

HID type headlight: 

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