Air Bag Light and Other Problems

Hi,
I am having problems with my Air Bag Light. The light only comes on after I have been driving on the highway for at least 30+ miles. When the light comes on, all of the lights on the car start to dim. When it has reached its limit, the car starts to decelerate. I have to pull over, then the lights come back on and I can drive again. Initially, it would do this every 10-15 miles. Then it was every 2 miles.

I have had the dealership and AutoZone check the battery, alternator, starter and the Airbag system to see if there is a problem. The battery was bad. I replaced it; drove 50+ miles and the airbag light came on again.

Any suggestions?

Hope you kept the old battery as a spare!
When you say "all the other lights on the car", you mean other indicator lights..not headlights. hey?
I'd say for some reason, the computer plays tricks, and stops working the injectors and/or timing too. With no other cues, I'd think of voltage feed to the computer: corroded wires - THAT happens, it did to me with Taurus - and bad grounds are a possibility. A wire "partly" shorted to ground -wrong routing - had that recently with my sons's car - also possible.
Removing the load for a few seconds cools the faulty connection/wire and it is ready to start anew...I'd use a voltmeter hooked up to monitor some key points while driving (starting with the lighter plug).

The other possibility is bad ECM....but I'd keep that as the last option.....just like the battery
.......they like so much to sell batteries .......
..and...add a few details about "all the lights"...will the heater blower go down too? and the wipers"? and the radio? every 2 miles ?!?!? obviously temperature related ! that puzzles me....do you have a 1000+ watt sound system that you shut down when you pull-off ?

Thanks for your response,

When I say "all lights," I mean interior lights dim, the CD player goes off, the windshield wipers move in slow motion, as if they are trying to stop. This only happens when I have travelled in excess of 30+ miles. I have no problems in the city.

I have posted diagrams that I had grabbed from KIA before they would ask money for it...may be you will be able to make some sense out of that...I had thought of poor contact in the ignition key switch - it does happen, I had 2 cars exhale smoke and smell from there (both Fords) with some similar effects, but if you had had such symptoms, you would have told.....
Check this out in the mean time:
www.avigex.ca/kia/fuseboxdetail.pdf
www.avigex.ca/kia/powerdistrib.pdf

Chack all the wires and connections at the positive distribution point at the end of the heavy gauge wire coming from the battery positive termional...look for corroded wires, loose connections....
that really looks like a poor/degraded contact or conductor: wipers have direct contact to the battery through the ignition switch...I 'm almost sure some burnt odor will come from somewhere sometime....keep the fire extinguisher handy.....

it really sounds like an altenator problem thou
also there was a problem on -99 with the harness just below the intake manifold it would get hot and cause grounds to arc ( two plugs below the planum)

I just had the same problem with my 01 Sportage. It is the alternator! I did a simple test with a volt meter available anywhere that shows DC volts. Put the leads across the battery. Should be 12 to 12.3 volts without starting it up. After you start it, it should be at least 1 to 1.25 volts higher than the battery by itself IE: 13 volts or more. HOWEVER, it will show that at idle. But after it runs for maybe 2 minutes, rev it up and you will see the voltage GO DOWN! even less than 12 volts. This will slowly drain your battery until it starts to show all those low voltage symptoms like the air bag light comes on, the radio cuts out, power windows move really slow, wipers slow, and at night, your headlights will dim. All this happens slowly so you don't notice it untill you got problems. The alternator is reverse charging. The faster you go, the less it charges. Believe me I didn't think this could happen. No alternator or battery light on the dash comes on either because it still charges the system at idle. Test it and you will not believe your eyes. Autozone to the rescue. Works great now.