2003 silverado 1500 5.3L gas with a P0420 code, inefficient catalytic bank 1... i have no other codes...what elso can I check , meaning what can i start testing to troubleshoot and repair this
im not burning oil, im not losing any coolant, it runs relativlely strong except at times it
runs a little rough. what also can I check on ? could you walk me thru the diagnostic
process to get my trucki back in shape?