Okay...i guess the LSD in Fortuner will be electronic and not mechanical. Also, i've checked - even the Auto LSD coming in Fortuner is not operable at the same time as Mechanical Diff lock. It only engages in 2WD when VSC is turned off (this activates LSD and a light will appear in the instrument cluster).
As per technical documentation I have seen for IMC Fortuner, A-TRC exists in Fortuner Sigma4. A-TRC automatically kicks in when the vehicle is put into 4WD HI and 4WD LO. A-TRC is built into the VSC system. Older cars used to have separate A-TRC button (talking in general, not specific to Fortuner):
This is the info I have sourced:
Auto LSD requires specific operating conditions:
• While TRAC/A-TRAC operate automatically, the driver must manually turn on Auto LSD. (Turning Auto LSD on turns TRAC off.)
• On 4WD vehicles, Auto LSD only operates when the vehicle is being driven in 2WD mode.)
• Because Auto LSD and Rear Differential Lock perform similar functions, vehicles may have one system or the other, but not both.
What’s the difference between TRC and A-TRC?
In H2, TRC engages when it detects a loss of traction at the rear wheels. TRC cuts engine power to restore traction and then can apply braking to move power across the rear axle
In H4 or L4, A-TRC engages when the system detects a loss of traction in any of the 4 wheels.
Existing brochures do not have A-TRC shown but I have confirmed that A-TRC in available, even in current Fortuner.