LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 1998 >> LS 400 >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control System >> Trouble Shooting
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Trouble Shooting

NOTE: Ensure multiplex system is okay prior to trouble shooting body control system. See MULTIPLEX CONTROL SYSTEM article.
TROUBLE SHOOTING SYMPTOMS

Problem Inspect
Lock Or Unlock Cannot Be Operated With Door Lock Control Switch (3) Body Control ECU No. 1
Lock Or Unlock Cannot Be Operated With Door Lock Control Switch (1) Passenger Door Lock Control Switch Circuit
Lock Or Unlock Cannot Be Operated With Door Lock Control Switch (2) Passenger Door ECU
Lock Or Unlock Cannot Be Operated With Door Lock Control Switch (1) Power Window Master Switch Circuit
Lock Or Unlock Cannot Be Operated With Door Lock Control Switch (2) Driver Door ECU
Door Key Link Function Does Not Operate (2) Passenger Door ECU
Door Key Link Function Does Not Operate (1) Driver Door Key Lock & Unlock Switch Circuit
Door Key Link Function Does Not Operate (2) Driver Door ECU
Door Key Link Function Does Not Operate (3) Body Control ECU
Door Key Link Function Does Not Operate (1) Passenger Door Key Lock & Unlock Switch Circuit
Key Confinement Prevention Function Does Not Operate (1) Key Unlock Warning Switch Circuit
Key Confinement Prevention Function Does Not Operate (3) Body Control ECU
Luggage Compartment Opening Function Does Not Operate (3) Body Control ECU
Luggage Compartment Opening Function Does Not Operate (1) Luggage Compartment Door Opener Motor Circuit
Luggage Compartment Opening Function Does Not Operate (1) Luggage Compartment Door Opener Switch Circuit
(1) Perform appropriate circuit test under CIRCUIT TESTS. If more than one circuit test is listed, perform tests in order listed.
(2) Perform PIN VOLTAGE TESTS in DOOR LOCK CONTROL SYSTEM article. If more than one pin voltage test is listed, perform tests in order listed.
(3) Perform appropriate PIN VOLTAGE TESTS. If more than one pin voltage test is listed, perform tests in order listed.
TROUBLE SHOOTING SYMPTOMS

Problem Inspect
Wireless Door Lock Control System Does Not Operate (2) Key Unlock Warning Switch Circuit
Wireless Door Lock Control System Does Not Operate (2) Wireless Door Lock Tuner Circuit
Wireless Door Lock Control System Does Not Operate (3) Body Control ECU
Wireless Door Lock Control System Does Not Operate (1) Wireless Door Lock Transmitter
Lock Or Unlock Function Does Not Operate (3) Body Control ECU
Lock Or Unlock Function Does Not Operate (2) Passenger Door Key Lock & Unlock Switch Circuit
Lock Or Unlock Function Does Not Operate (2) Passenger Door Unlock Detection Switch Circuit
Lock Or Unlock Function Does Not Operate (2) Right Rear Door Unlock Detection Switch Circuit
Lock Or Unlock Function Does Not Operate (4) Passenger Door ECU
Lock Or Unlock Function Does Not Operate (4) Right Rear Door ECU
Lock Or Unlock Function Does Not Operate (2) Driver Door Key Lock & Unlock Switch Circuit
Lock Or Unlock Function Does Not Operate (2) Driver Door Unlock Detection Switch Circuit
Lock Or Unlock Function Does Not Operate (2) Left Rear Door Unlock Detection Switch Circuit
Lock Or Unlock Function Does Not Operate (4) Driver Door ECU
Lock Or Unlock Function Does Not Operate (4) Left Rear Door ECU
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (4) Right Rear Door ECU
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (2) Driver Door Courtesy Light & Courtesy Switch Circuit
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (2) Left Rear Door Courtesy Light & Courtesy Switch Circuit
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (4) Driver Door ECU
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (4) Left Rear Door ECU
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (3) Body Control ECU
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (2) Passenger Door Courtesy Light & Courtesy Switch Circuit
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (2) Right Rear Door Courtesy Light & Courtesy Switch Circuit
Auto Lock Function Operates When Any Door Is Opened Within 30 Seconds After Unlocking All Doors With Wireless Door Lock Control System (4) Passenger Door ECU
Wireless Door Lock Operates, But Buzzer Does Not Sound (2) Wireless Door Lock Buzzer Circuit
Wireless Door Lock Operates, But Buzzer Does Not Sound (3) Body Control ECU
Buzzer Sounds, But Wireless Door Lock Function Does Not Operate (3) Body Control ECU
Luggage Compartment Door Opener Does Not Operate Properly (2) Luggage Compartment Door Opener Motor Circuit
Luggage Compartment Door Opener Does Not Operate Properly (3) Body Control ECU
(1) Check transmitter operation. See REMOTE KEYLESS ENTRY SYSTEMS article.
(2) Perform appropriate circuit test under CIRCUIT TESTS. If more than one circuit test is listed, perform tests in order listed.
(3) Perform appropriate PIN VOLTAGE TESTS. If more than one pin voltage test is listed, perform tests in order listed.
(4) Perform PIN VOLTAGE TESTS in DOOR LOCK CONTROL SYSTEM article. If more than one pin voltage test is Listed, perform tests in order listed.
TROUBLE SHOOTING SYMPTOMS

Problem Inspect
System Cannot Be Set (1) Anti-Theft Indicator Circuit
System Cannot Be Set (1) Driver Door Courtesy Light & Courtesy Switch Circuit
System Cannot Be Set (1) Left Rear Door Courtesy Light & Courtesy Switch Circuit
System Cannot Be Set (1) Driver Door Unlock Detection Switch Circuit
System Cannot Be Set (1) Left Rear Door Unlock Detection Switch Circuit
System Cannot Be Set (2) Left Rear Door ECU
System Cannot Be Set (1) Key Unlock Warning Switch Circuit
System Cannot Be Set (1) Passenger Door Courtesy Light & Courtesy Switch Circuit
System Cannot Be Set (1) Right Rear Door Courtesy Light & Courtesy Switch Circuit
System Cannot Be Set (1) Passenger Door Unlock Detection Switch Circuit
System Cannot Be Set (1) Right Rear Door Unlock Detection Switch Circuit
System Cannot Be Set (1) Luggage Compartment Door Courtesy Switch Circuit
System Cannot Be Set (2) Passenger Door ECU
System Cannot Be Set (2) Right Rear Door ECU
System Cannot Be Set (3) Body Control ECU
System Cannot Be Set (1) Engine Hood Courtesy Switch Circuit
System Cannot Be Set (2) Driver Door ECU
System Cannot Be Canceled When Ignition Is In ON Position (1) Key Unlock Warning Switch Circuit
System Cannot Be Canceled When Ignition Is In ON Position (4) Ignition Switch Circuit
System Cannot Be Canceled When Ignition Is In ON Position (3) Body Control ECU
System Does Not Cancel When Luggage Compartment Door Is Opened With Key (1) Luggage Compartment Door Courtesy Switch Circuit
System Does Not Cancel When Luggage Compartment Door Is Opened With Key (3) Body Control ECU
Headlights Do Not Operate Properly With System (1) Headlight Relay Circuit
Taillights Do Not Operate Properly With System (3) Body Control ECU
Taillights Do Not Operate Properly With System (3) Body Control ECU
Taillights Do Not Operate Properly With System (1) Taillight Relay Circuit
Hazards Do Not Operate Properly With System (1) Hazard Switch Circuit
Anti-Theft Horn & Standard Horn Does Not Sound (3) Body Control ECU No. 1
Anti-Theft Horn & Standard Horn Does Not Sound (1) Standard Horn Circuit
Anti-Theft Horn & Standard Horn Does Not Sound (1) Anti-Theft Horn Circuit
Anti-Theft Horn & Standard Horn Does Not Sound (3) Body Control ECU
During Warning Condition, System Cannot Be Canceled By Unlocking Door With Key (1) Driver Door Key Lock & Unlock Switch Circuit
During Warning Condition, System Cannot Be Canceled By Unlocking Door With Key (1) Passenger Door Key Lock & Unlock Switch Circuit
During Warning Condition, System Cannot Be Canceled By Unlocking Door With Key (2) Passenger Door ECU
During Warning Condition, System Cannot Be Canceled By Unlocking Door With Key (2) Driver Door ECU
During Warning Condition, System Cannot Be Canceled By Unlocking Door With Transmitter (5) Wireless Door Lock Transmitter
During Warning Condition, System Cannot Be Canceled By Unlocking Door With Transmitter (1) Wireless Door Lock Tuner Circuit
During Warning Condition, System Cannot Be Canceled By Unlocking Door With Transmitter (3) Body Control ECU
During Warning Condition, System Cannot Be Canceled By Turning Ignition To ACC Or ON Using Key (4) Ignition Switch Circuit
During Warning Condition, System Cannot Be Canceled By Turning Ignition To ACC Or ON Using Key (1) Key Unlock Warning Switch Circuit
During Warning Condition, System Cannot Be Canceled By Turning Ignition To ACC Or ON Using Key (3) Body Control ECU
During Warning Condition, System Cannot Be Canceled By Turning Ignition To ACC Or ON Using Key (3) Body Control ECU
Horns Sounded For More Than 60 Seconds (3) Body Control ECU
(1) Perform appropriate circuit test under CIRCUIT TESTS. If more than one circuit test is listed, perform tests in order listed.
(2) Perform PIN VOLTAGE TESTS in DOOR LOCK CONTROL SYSTEM article. If more than one pin voltage test is listed, perform tests in order listed.
(3) Perform appropriate PIN VOLTAGE TESTS. If more than one pin voltage test is listed, perform tests in order listed.
(4) Check ignition switch. See STEERING COLUMN SWITCHES article.
(5) Check transmitter operation. See REMOTE KEYLESS ENTRY SYSTEMS article.
TROUBLE SHOOTING SYMPTOMS

Problem Inspect
Wipers Do Not Operate (1) Wiper Switch Circuit
Wipers Do Not Operate (1) Wiper Motor Circuit
Washers Do Not Operate (2) Body Control ECU
Wipers Do Not Operate At Hi Speed (1) Washer Motor Circuit
Wipers Do Not Operate At Hi Speed (1) Washer Switch Circuit
Wipers Do Not Operate At Hi Speed (3) Wiring Harness
Wipers Do Not Operate When Washer Switch Is On (1) Wiper Switch Circuit
Wipers Do Not Operate When Washer Switch Is On (2) Body Control ECU
(1) Perform circuit test under CIRCUIT TESTS. If more than one circuit test is listed, perform tests in order listed.
(2) Perform PIN VOLTAGE TESTS. If more than one pin voltage test is listed, perform tests in order listed.
(3) Check wiring harness for opens or shorts. See WIRING DIAGRAMS in WIPER/WASHER SYSTEMS article. Repair or replace as necessary, and retest system operation.
TROUBLE SHOOTING SYMPTOMS

Problem Inspect
Automatic Light Control Does Not Operate (1) Light Sensor Circuit
Automatic Light Control Does Not Operate (1) Headlight Control Switch Circuit
Automatic Light Control Does Not Operate (2) Body Control ECU
Automatic Turn Off Does Not Operate (1) Ignition Switch Circuit
Automatic Turn Off Does Not Operate (1) Driver Door Courtesy Switch Circuit
Automatic Turn Off Does Not Operate (2) Driver Door ECU
Automatic Turn Off Does Not Operate (3) Body Control ECU
(1) Perform circuit test under CIRCUIT TESTS. If more than one circuit test is listed, perform tests in order listed.
(2) Perform PIN VOLTAGE TESTS in DOOR LOCK CONTROL SYSTEM article. If more than one pin voltage test is listed, perform tests in order listed.
(3) Perform PIN VOLTAGE TESTS. If more than one pin voltage test is listed, perform tests in order listed.
TROUBLE SHOOTING SYMPTOMS

Problem Inspect
Illuminated Entry Does Not Operate Properly (1) Illumination Circuit
Illuminated Entry Does Not Operate Properly (2) Body Control ECU
(1) Perform appropriate circuit test under CIRCUIT TESTS. If more than one circuit test is listed, perform tests in order listed.
(2) Perform appropriate PIN VOLTAGE TESTS. If more than one pin voltage test is listed, perform tests in order listed.
TROUBLE SHOOTING SYMPTOMS

Problem Inspect
A/C Control Panel & Multi Display Does Not Deteriorate (1) Rheostat Light Control Circuit
A/C Control Panel & Multi Display Does Not Deteriorate (2) Body Control ECU
(1) Perform circuit test under CIRCUIT TESTS. If more than one circuit test is listed, perform tests in order listed.
(2) Perform PIN VOLTAGE TESTS. If more than one pin voltage test is listed, perform tests in order listed.
scientia non olet · About LEMON Manuals