I got a PCM tune awhile back...Went in this last week to the Dealer to get warranty work done... (Rough Idle after starting cold engine and misfire codes) The dealer replaced the head... They also asked if someone ran a scan on my truck since something looked different during diagnostics. I told them when I got an oil change last they checked the error codes. The dealer did not notice the PCM tune in my case. Warranty work was covered... I did notice that my mileage is horrible now. 100 miles on a half tank... I was getting 145 with the bad head.

Not sure if the dealer messed with the PCM tune or if its due to the new head burning more gas. Hopefully after the new head wears in it will be back to wear I was before.... If anyone has any ideas Please let me know...

 

100 miles on a half tank is not right at all. 145 is not even that great... unless you're doing all city driving. I'm getting about 400 miles per tank all hwy driving. Perhaps 145/half tank is about right for city.. anyways perhaps the dealer tried to reflash the PCM noticing that something was off and it didn't take right. See if you can get the PCM place you used to reflash your PCM