Description & Operation

WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

WARNING: Vehicles are equipped with air bag supplemental restraint system. Before attempting repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in TOYOTA - AIR BAG RESTRAINT SYSTEMS article.

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

Multiplex control system consists of body control Electronic Control Unit (ECU), driver door ECU, front passenger door ECU, theft deterrent ECU and power seat ECU if equipped with driving position memory. The body control ECU controls the following systems:

Power door lock system.
Wireless door lock remote control system.
Automatic light control system.
Headlight off delay system.
Illuminated entry system.
Trunk release system.
Daytime running lights system.
Passenger seat belt warning system.

The body control ECU has a support role for control of theft deterrent system.

The theft deterrent ECU controls the theft deterrent system. The body control ECU, driver door ECU and front passenger door ECU provide a support role for control of theft deterrent system.

The driver door ECU and front passenger door ECU control the power window system and have a support role for:

Power door lock system.
Wireless door lock remote control system.
Illuminated entry system.
Mirror control system and memory system on models with driving position memory.

On models with driving position memory, the power seat ECU controls the mirror control system and memory system. The driver door ECU and front passenger door ECU have a support role for control of these operations.

The multiplex control system has a self-diagnostic function. The body control ECU is responsible for diagnosis of the multiplex system. Diagnostic Trouble Codes (DTCs) are stored by body control ECU for diagnosis and retrieval. All other ECUs within the multiplex system provide a support role to the body control ECU for diagnosis of the multiplex system. If multiplex communication system DTCs are not stored, the multiplex system is okay. Begin diagnosis with the system identified in customer complaint. See Figure. The OPEN DOOR indicator light can be used to display DTCs, or a scan tool can be connected to Data Link Connector 3 (DLC3) for retrieval of diagnostic information.