Bad sensor, Electrical?

History: 2 months ago, my low radiator fluid light would come on and my temp gauge would go towards the H. So, we filled the radiator with antifreeze and the temp went back to normal, also the low fluid light turned off. This kept happening so we thought that we had a radiator leak and needed a new one. We took out the radiator and checked for leaks. None. So we put the radiator back in the car. Now, a new problem. The “ETS off” light comes on. When this happens, the engine light also turns on, the temp gauge on the dash board registers at nothing, (as if there is no electricity registering the gauge) and the car shifts very hard. We did a systems check with the computer and it indicates that there is a problem with the sensor system. So we changed out the sensor. The car will run about 5 min with no warning lights and temp registers as normal and drives perfect (no hard shifting). After the 5 min, it seem like the new sensor turns bad, so all lights come on again along with the hard shifting... Do you think I have a short somewhere? If so, where and how should I check? I am a single mom of 3 and need to fix this the cheapest way possible...

I do have a multimeter if I need to check voltages.

If you need more information, please call 208-406-8512

Thank you for your response,

Angela Marler