from what i could look up: P1509 - Lake temperature circuit out of range
That has nothing to do with your speed sensor, it also shouldn't cause limp mode. the shop manual for my o6 RXT says limp mode is caused by the Engine Coolant Temperature Sensor, Exhaust Gas Temperature Sensor, or Oil Pressure Temperature Sensor. It isn't really clear on what other conditions may cause it but that's where I'd start.
If your engine is missing on acceleration there's a lot of things it could be. Easiest to start with is plugs/coils, but it could be CPS, bad ground, fuel pressure, clogged or faulty injectors, etc... Basically anything related to ignition and fuel.
