Getting very poor fuel milage around 6-8 mpg with little power. transmission seems to have hard shifts. No CEL just had map sensor replaced about 2000 miles ago. this is on our 06 3500 CC Lbz engine.. .Can anyone help

Is there smoke? Did it just start or is it bad since the sensor? Could you have gotten some bad fuel and then clogged the fuel filter? Is the fuel filter old?

fuel filter was replaced 500 miles ago it has been doing it since the map sensor. no smoke.

should also mention we tow about 10000

Was this the reason the MAP was replace in the first place? Mine acted like this once when I used the block heater when it was to warm out. I got a CEL light though and it limped. Tranny acted up too. Maybe a little history on why the MAP was replaced and if it ran fine after it would help?

it threw the cel and i took it to the dealer and they said the map sensor was bad we were like okay hasnt fixed anything still getting poor fuel milage. we have pnly had this truck for about 8000 miles and it has been in the shop 3 times. the 2nd time it was in it threw a turbo seal code dealer said it had to do with the block heater being pluged in and not needed. then 1 week later it threw the map sensor code.. now were here again

Check to make sure the sensor didn't get unplugged or loose.

Didn't the LBZs have the updated block heater that isn't supposed to cause a code. I know my 07 does. Agree with the rest. Check the connections and also check all of the intake and intercooler tubes/boots.