tach and temp sensor bounce around when blinkers are on

What is your question?

I noticed that sometimes when i turn my blinkers on when im driving that my tachometer and temp sensor readings bounce up and down, sometimes happens when i first start the car as well. its intermittent but you can notice that the temp sensor reading fluctuates slightly when i turn the blinkers on while the car is in motion, it did trip a code 17 once. any ideas on where to start?