P1258 code but not overheating

Question

So my Tahoe is throwing the P1258 code but it's not overheating, throws multiple sayings on the dash from Change oil to engine power reduced, but it's not overheating, I will let my tahoe sit for hours at a time and sometimes the minute I start it, it starts acting up saying stuff and sometimes causes a problem where it won't accelerate. The gauge goes from 210 to 260 sometimes but it's only for a few seconds then it goes back to 210. I've replaced the thermostat sensor, reset the codes, unplugged the battery, and had the oil changed. I'm pretty sure it's the ECU or the temperature coolant sensor, just want to narrow it down

Answer 1

P1258 Engine coolant temperature - protective mode active

When this code is set, the ECM will disable half of the fuel injectors, the engine will go into a reduce mode, there would be audible and instrument warning display,  Narrowing it down you would need to include the waterpump, if the engine show overheating the inlet hose would be hot to touch and the heater as well as the outlet would be cool to touch. Also if it is showing overheating condition you would need to see the operation of the cooling fan.  If you did not do the coolant temperature sensor, that would be the best step, rather than to condemn the ECM

Comments

Well see it's not actually over heating, I've replaced the sensor, and it's still messing up, the fans are on, and it's not hot under the hood.