Were you able to see that power appeared on the output of the TIPM to the tail lights?
Reference the link in post 3 from Moc.
C3 pin 8 is tail lamps (20Ga wht/vio)
C3 pin 13 is stop lamps (18Ga wht/orn)
"To measure is to know" that's why I've shared the wiring diagram.
As I've said in the first post: if no voltage present at TIPM output then check for short circuit to ground on that output. That is, with battery disconnected, measure its resistance to ground. I've saw wire's sleeves sliced that touched chassis metal along their way.
TIPM can act like automatic fuse and cut power to that output while short-circuit present. Once surge condition cleared it restore normal power output functionality.
Any cheap multi-meter can be used for that, easy 2 mins and no cost.
IF all good with TIPM and voltage present at its output, THEN dismantle the car to check wires interrupted, alarm issue or whatever else is stopping signal reaching tail lights.
Seems like it comes over a lighting signal from the headlamp switch, which I am having trouble finding in the service manual. Looks like one of those circuits where different voltages trigger different systems all over one wire.
No different voltages, headlamp switch is full digital, communication with the instrument cluster is done over one wire LIN bus