This morning when I started my car the warning light located directly under the temperature gauge came on. It is a diagram of a car with 6 dashes coming off the rear of the car. I do not have an owner's manual to check. What is this warning signal?

It may be the Engine Check Light.

https://www.jpauleytoyota.com/blog/what-are-toyota-dashboard-warning-lights-and-what-do-they-mean/

Aha, Catalytic converter Issue. Warning Symbol 29.

https://www.driven.co.nz/advice/advice/complete-guide-to-the-64-warning-lights-on-your-dashboard/

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Lumina V6, 2000 model after starting 5 to 6 mins temp gauge goes up slowly. Cooling fan is on. Coolant ok. If stopped the car and started again gauge needle comes down quickly to normal and then runs normal at any speed. It happens only first starting. I am suspecting temperature sender malfunction. Could not see the temp switch position to check its connection.On earlier models it is located directly under the thermostat. But if its bad it should throw a code making your check engine light come on. Sounds more like a thermostat problem. Even if its a new one they can fail.

Check the fuse panel under the dash and the power distribution panel under the hood for any blown out fuses.

Obviously it's temperature gauge light. Check for coolant level first. Then check for coolant leak. If coolant is leaking out of your car, the lower coolant levels in your engine will cause it to overheat. If you have your heater on and it starts blowing hot air instead of cool, your engine is low on coolant. This will cause to flash a warning light on your car's dashboard.

You mean by gadgets, warning lights and gauges? That would be from the ignition switch's run wire, the wire from the on position. This wire sends voltage to the ignition system, and to the dash for the warning lights and gauges-but not directly to the dash-the signal would reach the dash after being routed through the fuse panel to a fuse for the dash gauges and warning lamps. You need to check if that fuse is good.
Recall seeing any wiring diagram? The fuses are labeled either "hot at all times" or "hot in run or start". The fuses labeled hot in run or start are only sent power when the key is on, so power for those fuses are routed through, or turned on by the key being on. Depending on the car and its wiring set up, many will have relays that are turned on by the run wire, and power is then sent from the relay to that circuit's fuse in the fuse panel. This relay may be called the ignition relay. Or your car may have a different relay to send power from the run wire to the fuse panel.
The only way to figure yours out is to see a wiring diagram for it. Then you will see how power is sent from the ignition switch to the dash.
Wiring diagrams are almost always found in repair manuals. Check if your library has a manual for your car. Most libraries have quite a few repair manuals. Or parts stores sell repair manuals too, for about $25. Try to find a Haynes repair manual for your car. The other popular repair manual is from Chilton. My preference is Haynes, just my preference. I been burned by Chilton manuals sooo many times-incomplete wiring diagrams, incorrect information, incomplete information. Haynes are not perfect by any means, you want perfection-spend big bucks for a factory service manual ! In general, Haynes is more complete than Chilton.
OK, enough venting. If you have a test light, check for power at the fuse for the dash (may be labeled "gauges" or "instr pnl", something like that) with the key on. If it has power with key on, wire from the fuse goes to the dash. If that fuse has no power to it with key on, power has been lost between the ignition switch and that fuse-now you definitely need a wiring diagram to find the problem.

Symptoms point to the cluster microprocessor. How was it proven? See diagram below.

There are few help links provided to resolve this issue of dash board light not working.Click the link below to go through its procedure:-----Dash board lights not working? http://repairhelpcenter.blogspot.in/2012/02/dash-board-lights-not-working-on-gmc.html
----------- light in the dash blinks? http://repairhelpcenter.blogspot.com/2012/01/overdrive-light-in-dash-blinks.html
-----------Orange O/D warning light flashing on dash? http://repairhelpcenter.blogspot.com/2012/01/orange-od-warning-light-flashing-on.html
---------gauge on the dash quit working on? http://technoanswers.blogspot.com/2012/01/temperature-gauge-on-dash-quit-working.html---------No 4x4 light on dash? http://repairhelpcenter.blogspot.com/2011/12/no-4x4-light-on-dash.html
----------Digital Dash Display not working? http://schematicsdiagram.blogspot.com/2011/12/cadillac-seville-digital-dash-display.html
---------warning on dash and alarm sounds? http://schematicsdiagram.blogspot.com/2011/12/chevrolet-tahoe-hood-open-warning-on.html
---------Light Stays On dash of car? http://schematicsdiagram.blogspot.com/2011/06/brake-indicator-light-stays-on-dash-of.html
----------The ABS and Traction Control Lights stays ON dash of car? http://schematicsdiagram.blogspot.com/2011/06/abs-and-traction-control-lights-stays.html
----------warning lights remains steady on dash? http://schematicsdiagram.blogspot.com/2011/12/abs-brake-warning-lights-remains-steady.html
---------light bulb under dash replacement?

http://schematicsdiagram.blogspot.com/2011/12/heating-knob-light-bulb-under-dash.html

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Parking lights, tail lights and dash lights not working? http://technoanswers.blogspot.com/2012/01/parking-lightstail-lights-and-dash.html

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How to replace Instrument panel and dashboard?

http://repairhelpcenter.blogspot.in/2012/02/how-to-replace-instrument-panel-and.html

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Tail lights and dash light fuse keeps blowing? http://technoanswers.blogspot.in/2012/02/tail-lights-and-dash-light-fuse-keeps.html

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This will help.

Thanks.

These lights for the dash are controlled by a rheostat instrument control dimmer switch next to the main light switch for the headlights, it is either turned off (have seen this dozens of times) or it is defective. Below is a picture of the switch assembly I speak of. The thumb wheel next to the knob is the dimmer control.

temperature gauge is not reading correctly and the car is overheating due to a leak or a blockage in the coolant system.

REPLACE BUSTED FUSES