I'd say either a lack of coolant in the heater core or it is clogged. When flushing the core use very little pressure at first. If you use too much you can burst the seams and you'll then be replacing it.

 

My car dos the same thing. From what others have alrdy said i see this as normal. My car has a 180 temp and sits just above the first mark. If i idle it will climb to 230-240 then fans kick on and drops down and repeats till i drive. If im driving it drops back down to the first mark and stays.

 

Thanks for all the replies everyone! I was going to wait until my work week was over, but I was just too curious since I was getting heat when the car was at warmer temps, but not at cooler temps going down the road...went ahead and flushed the heater core (and the rest of the cooling system after, and now I have pretty toasty air at all times...so much thanks for that advice.

Regarding my confusion about the temps fluctuating in exactly the same fashion when the SES light was on and after the SES was resolved...I was greated w/ a SES light this morning when I started the car to work on it...bad cat (luckily my UPS man should show up w/ headers/y on Wed). Despite the SES light being on, the fans still cycled on and off as they normally would. I have no idea as to the hx of the tune on the PCM, or if this is a function that can be deleted by a tuner. Regardless, I will be getting a fresh tune this week for the headers.

Based on all the input from you all, and verifying temps were within normal range with my IR gun, I feel comfortable I can ignore my temp gauge unless it starts to head north of "normal." Thanks again to everyone for the input.

 

Most codes cause the fans to come to come on, but not all. If you have a tune where some codes were disabled, I would imagine the fans would not come on, either.