You need to do what rasmataz said. In addition, do exactly what the warning light is telling you to do; "check the gauges". If the idle speed is too low, engine oil pressure and charging system voltage will both be too low and will trigger the light to get your attention. If the light goes out when you raise engine speed, there's your proof there's nothing wrong other than the low idle.
The body computer has nothing to do with the engine. It's an over-complicated way to control power door locks, windows, and wipers.
If you have the 3.0L engine, they used to have trouble with an air passage getting plugged with carbon, but that's been less of a problem with modern fuels. My 1988 Grand Caravan has the 3.0L and its passage has never needed to be cleaned in its 210,000 miles. One clue to look for is called "idle flare-up". Without placing your foot on the gas pedal, the engine should run up to around 1500 rpm, then back down to 800 within a few seconds, when you start the engine. If it doesn't do that, or you have to hold the pedal down to get it to start, either the idle speed motor isn't working or the air passage it sits in is plugged with carbon. If you do get the idle flare-up but then it stalls, the passage and idle speed motor are working. You might just need to do the minimum idle relearn procedure.
Solving a running problem is almost unheard of on a Chrysler product by replacing the fuel filter. Of my three Caravans, I changed one at 180,000 miles because it started to leak; the other two are original. It's a long explanation, and you may not believe me, but the fuel filter passes the most fuel volume when you are coasting down from highway speeds and it passes very little fuel when you are accelerating. The symptom of a plugged filter is stalling when coasting. Holler back if you'd like an explanation of why this happens. It will take me an hour to type it up.
Finally, if you or the seller recently had the battery disconnected, you will need to do the idle relearn procedure. Basically, this means driving it at highway speed, then coasting for a minimum of seven seconds without touching the brake or gas pedal. Before this procedure is done, the engine computer doesn't know, (based on throttle position sensor voltage), when your foot is off the gas pedal and it must be in control of idle speed. Until it learns the minimum sensor voltage, it leaves control of idle speed up to you and your foot. I can't remember if you will get that idle flare-up when you start the engine when the idle relearn hasn't been done.
Sunday, March 22nd, 2009 AT 8:17 PM