Speedometer just stopped working with no notice

check the ground

Sometimes it looks crazy too. But first look for good grounds Battery, cluster gauge
you will have to retrieve the faulty code with a scanner that can read the code.

Hope it help

You have to check speed sensor,could be worn out.

try another horn they go bad also

this is in the speedometer unit itself. either purchase a known good part from an auto recycler or people still rebuild these. on these, they are individual little motors inside and they will probably just replace the speedo motor and reseal it. unfortunately you can not purchase these parts yourself.

if this is a digital speedo you need to replace it if normal then you need to replace the speedo cable. Or you could buy a cheap GPS they have speedos built into them and they work good for getting you from a to z and back to a as well

there could be a trans or speed sensor problem. I dont know about the light reminder ?? I would have a trans shop check it first.

I suspect you needto relace your coil pack. You are probably not running on all 4. the engine will run but only on 2 cylinders.
If missing replace coil pack. they go regularily on the 03/05 F style engines. You should be able to locate a good used one at a wreckers.

Pretty common on the 03-05 Sunfire instrument clusters. It's caused by the stepper motors on the cluster circuit board going bad but it can be fixed. Check out this page for more about how to get it fixed - Sunfire speedometer fix

From 2003 to 2006 GM - chevy , pontiac , buick , cadillac , had bad step motors inside the instrument clusters , causing gauges to no work or sporadically . Happened to my 2005 chevy cavalier , went to automotive salvage yard ,got a used one for $20.00 buck's . That was two year's ago , now problems !
How to repair GM Instrument Cluster Speedometer Gauge Stepper
Or you can buy the up graded stepper motors on eBay an fix it .