rear light warning indicator on Options

[ksporry]

Guys,
For a year or so, I have been driving around with a rear light warning indication on the instrument panel. The light comes on when i press the brake pedal and stays on until I switch the car off.
It seems to imply that at least one of the brake lights is out. However, this is not the case, all brake lights seem to be working fine.

Now there is a bit more to the wiring than just factory standard. At some point someone disconnected two brake lights. You should know that I have a japanese import that does not have a proper fog light on the back. Someone seems to have cut off the two inner brake lights. This however does not cause the problem. It shall become clear in a moment.
The light came on ever since some wanker garage wired in a light switch to use a "spare" rear brake light as fog light. He claimed that I have a fog light and therefore I HAVE to have a switch. However, it doesn't have a rear fog light, they are brake lights only. Anyway, he wired it as followed: he spliced into a Red-White wire on the right connector on the steering wheel (seems to be headlight-HI control line according to some Celica wiring diagrams). Interestingly this is not a high power line. he then ran the wire from the splice to a switch. the switch has a second wire running to the lamp and a third wire running to chassis. EXcept for the splice I think the installation itself seems ok though. I wonder if the splice is causing the brake system to get upset. However, I tried disconnecting the new wires from the switch completely, but that did not solve the problem. So even with the switch disconnected completely, it is stll lighting the warning light.

So now I am thinking if maybe a light bulb is actually making bad contact, resulting in the brake light functioning correctly, but the bad contact maybe causing the warning light to come on?
Anyone who can shed some light on this?

[trdproven]

I would doublecheck and redo all the wiring.