Relevant for D-Max & BT-50 (2020+)
Using the locking tab as a reference, have it facing down and work from left to right.
1: Earth / Ground (black on the STEDI harness)
2: Dash Lights - Normally connected to dash light circuit to be on when your dash lights are active.
3: Relay - Connect to your relay or accessories (blue on STEDI harness)
4: Source - Connect from your source with an inline fuse (white on STEDI harness)