The P1281 is not just that the coolant is cold, it is a signal that the coolant temperature did not rise from a low value to a high value fast enough. Because fuel enrichment and exhaust emissions are higher during the start and warm-up period, the OEMs must get the engine out of the cold start algorithm as quickly as possible.
I experienced this once when the thermostat failed open.
From a lubricant perspective this is also problematic. Some experienced people will note that when the thermostat is a lower temperature, the engine runs better because the ECU runs richer. However, this introduces more fuel dilution and (as a product of normal combustion) water condensation to the oil. The fuel lowers the lubricity and viscosity of the oil; the water attracts many additives and renders them ineffective. In normal operation, most of the fuel and water is driven off when the oil temperature gets high enough, something most drivers cannot know because there isn't an oil temperature gauge. Truly severe case - look at the underside of the oil fill cap during the winter season and notice the white mayonnaise in the rocker cover. That is a water-oil emulsion.
While the above are facts, the following is opinion: In the old days of carburetors and heated intake manifolds, the coolant would run through the manifold to get from one bank of a V engine to the other. In that case, the coolant helped warm-up, but because it heated the intake charge, would decrease the air consumption at WOT. In this case a colder thermostat would allow greater power because the air entered the combustion chamber at lower temperatures. With the current Viper engine, the thermostat is separate from the intake manifold, the fuel is injected at each cylinder, and the intake runners are off of the block, so a colder thermostat doesn't lower the intake charge temperature. Unless the lower thermostat fools the ECU "a lot" I don't think it should make any difference. Again, my opinion is to allow the coolant to rise to the thermostat temperature and then limit the excursions above that. Don't think you are eliminating high temperatures excursions by opening the thermostat sooner if the cooling system is marginal.
Last comment - another argument from the physics side. If the head and block are cooler, they draw heat from the combustion chamber, decreasing power. If the head and block are hotter, they don't **** heat out and keep more energy available for gas expansion and work on the piston. Pro racers (a race longer than 0.25 miles) run around 230F coolant.
BUT, I was looking for more info as to what the codes mean and whether I should be worried... Thanks nonetheless.
