hi all, im morat, and i have a problem,i keep getting a code of 118, on my code scanner,high temp sensor,ive changed the sensor and the gauge and cleared the code,when i clear the code and let the car idle to warm up to chheck if the temp gauge is working, itll set there for a few mins on 100 and then suddenly shoot up to, ill say , normal operating temp,run there for a few mins, then itll drop down to the peg and the cooling fan kicks on and it codes again. like ive said i have changed the temp sensor and gauge already. could this be a possible computer issue?? thanks

by the way i am dealing with a 1999 pontiac sunfire with a 2.2 auto