GM’s recent V8 engines have experienced check engine issues caused by faulty valve springs
The issue is addressed in a recent service bulletin from GM
GM vehicles equipped with V8 engines may show a service engine light as well as experience various other problems including misfires and odd noises. The issue is apparently caused by faulty valve springs according to a recent GM service bulletin.
The bulletin instructs GM technicians to check for a broken valve spring and perform a cylinder leak test if needed. If the test proves conclusive, service departments are instructed to replace all valve springs if the vehicle was built between June 1 and September 15 2020.
According to GM Authority, this only applies to the L87, LT1, LT2, and LT4 6.2-litre V8 GM engines. For L82, L84, and L8T V8 engines, dealers are required to replace the problematic valve spring.