Backup Boost Converter Circuit [12/2019 - 10/2022]: Description

A backup boost converter is built into the engine stop and start ECU. The backup boost converter helps maintain the power source voltage when the engine is restarted by stop and start control.

This prevents various functions such as the navigation system or audio and visual system from malfunctioning if the power source voltage drops due to the battery voltage dropping when the engine is restarted by stop and start control.

If any DTCs are output, troubleshoot the DTCs first.

HINT: 

A relay function and fuse function are provided in the backup boost converter.

If there is a malfunction in any of the electrical system circuits connected to the backup boost converter, the fuse and relay functions shut off the malfunctioning circuit to protect other circuits (remains shut off until next trip).

When the electrical system circuit is shut off, power to the circuit is cut off, causing any systems connected to the circuit to be disabled.

The fuse function is reset* when the ignition switch is turned off. If the malfunction still exists in the electrical system circuit that has been shut off by the relay function, it will be shut off again by the relay and fuse functions the next time the ignition switch is turned to ON.

*: A semiconductor fuse self resets according to electric signal.

The backup boost converter supplies power to: 

• Electronically controlled brake system
• Power steering system
• Meter / gauge system
• Audio and visual system
• Navigation system
• Rear seat entertainment system
• Digital rear-view mirror system
• Auto glare-resistant EC mirror
• Tire pressure warning system
• Lighting system (INT)
• Telematics system
• Air conditioning system
• CAN communication system
• Toyota safety sense
• Parking support alert system
• Headup display system
• Blind spot monitor system
• Fog light assembly

The external backup boost converter (eco run vehicle converter assembly) supplies power to: 

• Navigation system