Thermostat is not difficult to replace, but I would check the coolant level (when it's cool) and make sure its to the top. The older Sedonas are notorious for the rear heater coolant lines corroding and leaking out and could cause the light to come on. If its low, I'd start looking for a coolant leak.Engine light just came on in 04 Sedona. Diag says either coolant temp sensor or thermostat sticking open and that it's running cooler than it should. Is this a hard fix?
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