The car light on top has been on for awhile with no visible issues all lights still worked. now all of a sudden my front right turn signal isn't working the rear does. but for some reason it's making both marker lights blink when I turn my right turn signal on and I can't figure out why! I can't even figure out why this light came on. can anyone help me out with this what is this light for I assume to inform u a bulb is out but it's been in for months and all bulbs are fine. any information is appreciated thanks

 

This can be caused by the bulb, even if it is working. When I changed a burnt out tail light bulb with a spare I had (generic crappy one) my idiot light came on as well. When I switched to a higher quality bulb this went away. I have a feeling it's due to voltage or resistance of the bulb or at least my situation was from that. Also check to make sure no wires are pinched for the harnesses as a short can cause the taillight warning to come on. Hope that helps.

 

That does help I got those cheap led bulbs from China what is the best bright tail and drl bulbs for the sc400 I have a 96. would tag lights also cause that light to come on?

 

Yes, the license plate lights can turn the dash light on.

 

The 3rd brake light can signal it, too. My SC300 had a winged trunk added at some point, but the P.O. never plugged the spoiler in, presumably not knowing they're all wired for it and have the bundle tucked away in the trunk. So, I removed the parcel shelf brake light and plugged in the trunk spoiler. As soon as I touch the brake pedal, the dash light comes on. (Wrong lamp failure module.) Plug the parcel shelf light back in, no problem even with the trunk spoiler installed. So, I imagine it's possible for one bulb being out in the brake light to signal the warning light.

That said, I still have a second unsolved issue triggering the warning light, whenever I turn on the headlights. It could be a working bulb not offering the right resistance like vipsoarer said. The only bulb I've found that's out is one of my fog lights. Anyone know if that can trigger it, even with them not turned on?

 

It indicates you have a faulty bulb. If your signals are acting up that's probably your answer. Change then out, it's extreamly easy and cheap. Also the 3rd brake light as stated above is extremely coming to go out and cause this light