My cousin info me that his 2003 gmc serria 1500hd 6.0 around 160,000 miles. He drove and dying on him. Say cluster show "reduce power" he waited a min try crank again. Run again. Wonder what it cause?? Knock sensor? Crank position sensor?

 

Pull codes.

 

It keep engine light off when you crank up again

 

You'll have pending codes set, and you don't have to start the engine to read codes.

 

Yes, you have to read the codes. A number of problems can cause the vehicle to go into reduced power or limp mode.