LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2003 >> SC 430 >> Repair and Diagnosis >> External Pages >> Different car >> Section 368 (Body Control System - Diagnosis) >> Problem Symptoms Table
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Problem Symptoms Table

WARNING: This page is about a different car, the 2003 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.

LIGHTING SYSTEM: 

SYMPTOM

Symptom Suspected Area See page
Headlight does not come on. (Low beam)
  1. Light control switch circuit
  2. Headlight relay circuit
  3. Combination switch
  4. Body ECU (Main)
  1. Light Control Switch Circuit 
  2. Headlight Relay Circuit 
  3. INSPECTION
  4. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Headlight system does not operate. (HI beam or Flash)
  1. Headlight dimmer switch circuit
  2. Light control switch circuit
  3. Combination switch
  4. Body ECU (Main)
  1. Headlight Dimmer Switch Circuit 
  2. Light Control Switch Circuit 
  3. INSPECTION
  4. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Automatic light control system does not operate.
  1. Light control sensor circuit
  2. Light control sensor
  3. Body ECU (Main)
  1. DTC B1244 Light Sensor Circuit Malfunction 
  2. INSPECTION
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Taillight system does not come on.
  1. Taillight relay circuit
  2. Taillight circuit
  3. Light control switch circuit
  4. Combination switch
  5. Body ECU (Sub)
  6. Body ECU (Main)
  1. Taillight Relay Circuit 
  2. Taillight Circuit 
  3. Light Control Switch Circuit 
  4. INSPECTION
  5. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
  6. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Stop light system does not come on.
  1. Stop light switch
  2. Stop light circuit
  3. Body ECU (Sub)
  1. INSPECTION
  2. Stop Light Circuit 
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

HAZARD WARNING SYSTEM: 

SYMPTOM

Symptom Suspected Area Action
Hazard warning light does not come on.
  1. Hazard switch
  2. Flasher relay
  1. INSPECTION
  2. INSPECTION

ILLUMINATION LIGHT SYSTEM: 

SYMPTOM

Symptom Suspected Area Action
Illumination light does not come on.
  1. Power source circuit (Body ECU (Sub))
  2. Power source circuit (Body ECU (Main))
  3. Illumination circuit (Body ECU (Main) control)
  4. Illumination circuit (Body ECU (Sub) control)
  5. Body ECU (Sub)
  6. Body ECU (Main)
  1. Power Source Circuit (Body ECU (Sub)) 
  2. Power Source Circuit (Body ECU (Main)) 
  3. Illumination Circuit (Body ECU (Main) Control) 
  4. Illumination Circuit (Body ECU (Sub) Control) 
  5. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
  6. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Brightness does not change even when rheostat is turned on. (All)
  1. Light control rheostat
  2. Body ECU (Main)
  1. INSPECTION
  2. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Door courtesy light does not come on.
  1. Door courtesy switch circuit
  2. Body ECU (Main)
 Door Courtesy Switch Circuit 
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

DRIVER SEAT BELT SYSTEM: 

SYMPTOM

Symptom Suspected Area Action
Driver seat belt warning does not come on.
  1. Driver buckle switch circuit
  2. Combination meter
  3. Body ECU (Main)
  1. Driver Seat Buckle Switch Circuit 
  2. INSPECTION
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

POWER DOOR LOCK CONTROL SYSTEM: 

SYMPTOM

Symptom Suspect Area Action
All the doors can not be locked or unlocked.
  1. Power source circuit (Body ECU (Main))
  2. Body ECU (Main)
  1. Power Source Circuit (Body ECU (Main)) 
  2. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Driver side door lock does not operate.
  1. Door lock motor circuit
  2. Body ECU (Main)
  1. DOOR LOCK MOTOR CIRCUIT
  2. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Door key related function cannot be done.
  1. Door key lock and unlock switch circuit
  2. Door courtesy switch circuit
  3. Body ECU (Main)
  1. DOOR KEY LOCK AND UNLOCK SWITCH CIRCUIT
  2. Door Courtesy Switch Circuit 
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Key confinement prevention function does not operate.
  1. Door courtesy switch circuit
  2. Door unlock detection switch circuit
  3. Body ECU (Main)
  1. Door Courtesy Switch Circuit 
  2. DOOR UNLOCK DETECTION SWITCH CIRCUIT
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

POWER SEAT CONTROL SYSTEM: 

SYMPTOM

Symptom Suspect Area Action
Driving position memory system does not operate.
  1. Memory switch circuit (w/ memory)
  2. Power seat control ECU
  3. Body ECU (Main)
  1. Memory Switch Circuit (W/memory) 
  2. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

WIRELESS DOOR LOCK CONTROL SYSTEM: 

SYMPTOM

Symptom Suspect Area Action
Wireless door lock does not operate.
  1. Wireless door lock control circuit
  2. Wireless door lock tuner
  3. Body ECU (Main)
  1. Wireless Door Lock Control Circuit 
  2. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Wireless door lock buzzer does not operate.
  1. Wireless door lock buzzer circuit
  2. Body ECU (Main)
  1. WIRELESS DOOR LOCK BUZZER CIRCUIT
  2. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

REAR WIPER SYSTEM: 

SYMPTOM

Symptom Suspect Area Action
Rear wiper system does not operate.
  1. Door courtesy switch circuit (back door)
  2. Power source circuit (Body ECU (Sub))
  3. Rear wiper switch circuit
  4. Rear wiper motor circuit
  5. Body ECU (Sub)
  1. Door Courtesy Switch Circuit 
  2. Power Source Circuit (Body ECU (Sub)) 
  3. Rear Wiper Switch Circuit 
  4. Rear Wiper Motor And Relay Circuit 
  5. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Rear washer linked function does not operate.
  1. Rear wiper switch circuit
  2. Body ECU (Sub)
  1. Rear Wiper Switch Circuit 
  2. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
oror
Vehicle speed switching function does not operate.
  1. Door courtesy switch circuit (back door)
  2. Speed signal circuit
  3. Body ECU (Sub)
  4. Body ECU (Main)
  1. Door Courtesy Switch Circuit 
  2. Speed Signal Circuit 
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
  4. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Reverse linked function does not operate.
  1. Door courtesy switch circuit (back door)
  2. Reverce signal circuit
  3. Front wiper position circuit
  4. Body ECU (Sub)
  1. Door Courtesy Switch Circuit 
  2. Reverse Signal Circuit 
  3. FRONT WIPER POSITION CIRCUIT
  4. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE

OTHERS: 

SYMPTOM

Symptom Suspect Area Action
Key unlock warning system does not operate.
  1. Key unlock warning switch circuit
  2. Key unlock warning switch
  3. Combination meter
  4. Body ECU (Main)
  1. Key Unlock Warning Switch Circuit 
  2. INSPECTION
  3. INSPECTION
  4. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Parking brake indicator does not come on.
  1. Parking brake switch circuit
  2. Combination meter
  3. Body ECU (Main)
  1. Parking Brake Switch Circuit 
  2. CIRCUIT
  3. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
Open door warning light does not come on.
  1. Open door warning light circuit
  2. Door courtesy switch
  3. Combination meter
  4. Body ECU (Main)
  1. Open Door Warning Light Circuit 
  2. INSPECTION
  3. CIRCUIT
  4. HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE
scientia non olet · About LEMON Manuals