PO 300 error in GMC Yukon

Question

Changed all plugs and wires. Still running rough.  Still same error. What else is wrong?

Answer 1

HI there,

This code can come up for several reasons. You may have issues with a leaking intake manifold gasket, low fuel pressure, timing issues, the cap and rotor could also need replacement. Depending on the mileage you could also be looking at internal cylinder issues and valve problems. This can be a tricky code to track down since the computer is unable to pinpoint which cylinders are misfiring. Check for intake manifold leaks and fuel pressure next.