Body Ecu No. 2 System Operation Check

WARNING: This page is about a different car, the 2003 Lexus GS 430, 2003 Lexus GS 300, 2002 Lexus GS 430, and 2002 Lexus GS 300. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Prior to trouble shooting body control system, check multiplex communication system for proper operation and stored codes. The body control ECU's store Diagnostic Trouble Codes (DTCs) for the multiplex communication system and is the access point to communicate with other ECUs on the multiplex communication bus (circuit). See MULTIPLEX COMMUNICATION SYSTEM article in COMMUNICATION DEVICES.

Trouble shooting of a body ECU No. 2 control system complaint begins with verification of the customer problem. If problem occurs, go to step 3. If problem does not occur, go to next step.
If problem does not occur, review conditions under which problem occurred for customer and try to duplicate those conditions. For example, if the problem occurs on rainy days or during high humidity conditions, sprinkle water onto vehicle and see if malfunction occurs. DO NOT sprinkle water directly into engine compartment or onto electronic components. Visually inspect for signs of mechanical and electrical damage. Inspect for blown fuses and damaged relays. Inspect for loose or corroded connections, damaged wiring harness and/or switches. Check for a broken or partially broken wire inside insulation, which could cause system malfunction but prove good in a continuity/voltage check with system disconnected. Ensure any aftermarket electronic equipment is properly installed. If fault is found, repair as necessary.
Inspect the multiplex communication system and confirm that there is no trouble by the basic inspection and DTC check. See PRE-CHECK under SELF-DIAGNOSTIC in MULTIPLEX COMMUNICATION SYSTEM article in COMMUNICATION DEVICES.

Determine problem symptom. See BODY ECU NO. 2 PROBLEM SYMPTOM INDEX table.

BODY ECU NO. 2 PROBLEM SYMPTOM INDEX

Symptom

Suspected Area ⁽¹⁾

Illuminated Entry

Illuminated Entry Does Not Operate

⁽²⁾⁽³⁾

Light Control

Automatic Light Control Does Not Operate

⁽⁴⁾⁽⁵⁾⁽³⁾

Auto Turn-Off Does Not Operate

⁽⁶⁾⁽⁷⁾⁽⁸⁾⁽³⁾

Other

Does Not Turn Off Driver Seat Belt Warning Light

⁽⁹⁾⁽³⁾

Clock Will Not Deteriorate Light

⁽¹⁰⁾⁽³⁾

Body ECU No. 2 Does Not Operate

⁽¹¹⁾⁽³⁾

⁽¹⁾	Perform test procedures in order listed under suspected area.

⁽²⁾	Check the illumination circuit. See ILLUMINATION CIRCUIT under CIRCUIT TESTS.

⁽³⁾	Check the body ECU No. 2. See PRE-CHECK under SELF-DIAGNOSTIC SYSTEM under MULTIPLEX COMMUNICATION SYSTEM article in COMMUNICATION DEVICES.

⁽⁴⁾	Check the light sensor circuit. See DTC B1244/44: LIGHT SENSOR CIRCUIT MALFUNCTION under DIAGNOSTIC TESTS in MULTIPLEX COMMUNICATION SYSTEM article in COMMUNICATION DEVICES.

⁽⁵⁾	Check the headlight control switch circuit. See LIGHT CONTROL SWITCH CIRCUIT under CIRCUIT TESTS.

⁽⁶⁾	Check the driver's door courtesy switch circuit. See DOOR COURTESY LIGHT & COURTESY SWITCH CIRCUIT in AUTOMATIC HEADLIGHTS & LIGHTING article in HEADLIGHTS.

⁽⁷⁾	Check the ignition switch circuit. See STEERING COLUMN SWITCHES article.

⁽⁸⁾	Check the driver door ECU. See COMPONENT TESTS under POWER DOOR LOCKS, TRUNK LID & FUEL DOOR RELEASE article in DOOR LOCKS & ANTI-THEFT SYSTEMS.

⁽⁹⁾	Check the driver buckle switch circuit. See DRIVER BUCKLE SWITCH CIRCUIT under CIRCUIT TESTS.

⁽¹⁰⁾	Check the clock circuit. See CLOCK CIRCUIT under CIRCUIT TESTS.

⁽¹¹⁾	Check the power source circuit. See POWER SOURCE CIRCUIT (BODY ECU NO. 2) under CIRCUIT TESTS.

Inspect the circuits of the body ECU No. 2. See CIRCUIT TESTS .
After problem has been identified and repaired, confirm repairs. See CONFIRMATION TEST under SELF-DIAGNOSTIC SYSTEM.