Disconnect of speed sensor behind emblem

I can't answer your direct question, but personally, I'd pull the 12V power before messing with any of those sensors. I'd want to potentially avoid anything that might cause me to have to replace one or an ECU, not that that would happen. Just my $0.02. I'm sure the online shop manual states where it's required to pull power to those before disconnecting. It's a daily access price type of subscription.

 

The sensor behind the emblem is the millimeter wave radar sensor assembly. The Repair Manual (more info) says its beam axis has to be adjusted “When the front bumper is damaged or deformed due to an accident or contact with other objects, etc., or the bumper installation area on the body is repaired,” or “When the millimeter wave radar sensor assembly or No. 1 millimeter wave radar sensor bracket is replaced with a new one.” I don’t see anything that says adjustment is needed if you just remove and reinstall the original parts, even if you disconnect and reconnect the electrical connector to the radar sensor assembly.

The adjustment procedure requires a Toyota Techstream diagnostic system and two special service tools, Reflector C (09870-60040) and the Base Stand (09870-60010, sold in the 09870-60000 kit).

Whenever the front bumper assembly is removed and reinstalled, you’re supposed to calibrate the intelligent clearance sonar system. This also requires a Toyota Techstream diagnostic system, a digital angle gauge (Toyota 01815-00102, Bevel Box, or similar) and a special service tool, Attachment B (09989-00020).

You’ll also need the Techstream system, by the way, to change the grille shutter control mode to maintenance mode, which is the first step for removing the front bumper.

I think you may find it difficult to keep all of the electrical connectors attached, and in any case, the need for calibration arises because of the replacement or displacement of the parts, even if they remain connected.

I strongly endorse @Mark57's kind advice to disconnect the negative terminal of the auxiliary (12-volt) battery before doing any work; you don’t want the fan to come on or anything else to happen while your hands are nearby.