oil gauge is reading high all the time in my 2005 yukon xl
I believe that your problem originates with insufficient ground....the non- battery end of the 1/0 cable connects to the chassis/ground...this one must be cleaned with a wirebrush...and put a fresh battery in 5 years old and you must change it or start cooking the alternator then~~
Go to your local auto parts store have the codes read. They will do this for free. Then post the codes on here and we will help you more.