Technical Service Bulletin PIP4959G — 2015 BUICK LACROSSE

This Preliminary Information communication provides information to the technician with information regarding high misfire rates always on #1 cylinder. A customer may complain of misfires or roughness on cold start up with a P0300 diagnostic trouble code. Technician is to add coolant dye to the system and run the engine through warm up to circulate the dye. Pressurize the cooling system after a cold soak and inspect the cylinder with a bore scope for coolant dye. Dye is used to identify coolant over residual fuel being that might be left in the cylinder. The technician is not to replace the cylinder head as it will not correct this concern. In some cases it is necessary to remove the head for inspection. Do not replace the engine for small surface pock marks or a pitting appearance this is normal and do not connect to coolant passages. Usually if porosity is present there will be a break in the carbon ring. Only replace the engine if true porosity is found. Technician is to call Product Quality Center with the latest version of bulletin 02-07-30-029 if porosity is found and engine replacement is required.