Tdco ?

[DaveNY]

When last checked the TDCO on my truck after KOKO was -1.61 I liked it there and thought no more about it. I set a 261 code (TM and no boost fooler)and had some time and cleared the history with AE, checked everythng else a found The TDCO at -1.85. Im sure the temp was up when I set it and it was fully warm when checked. How does this value change? Something going wrong? The time frame is around 5mos. from set to check.
Dave