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I can find no P1798 code. There is a P1792 code that has to do with the transmission control module not getting the probler engine temperature information form the engine control computer. The light with the arrow pointing down is the low coolant light. You will need to top off the cooling system, this should fix the problem. Then check to see if there are any coolant leaks on the engine or radiator.
According to the manual, the light with the arrow pointing down means loss of power. And it definitely loses power. That is when the engine dies. It is just like turning the key off. I think the code was P1798, but it could have been P1789. I didn't write it down. Sorry.