One problem related to check engine light on has been reported for the 2018 GMC Sierra 1500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2018 GMC Sierra 1500 based on all problems reported for the 2018 Sierra 1500.
The speed of the truck will not increase. The rpms goes really high and the truck will not move into the next gear. The rear end of truck vibrates. I took this to the dealer and was told it is the transmission fluid is faulty. The check engine light does come on. I did not have the new transmission fluid changed because dealer said is cost $300 for the fluid and $100 for the labor and $168 for the diagnostics. So I still have the same problem. Also told you can not purchase this transmission fluid no where but GMC.