This bulletin applies to 2018 GMC Yukon and Yukon XL vehicles equipped with a 5.3L or 6.2L engine. A vehicle may have a concern of a misfire P0300 on Bank 1 that may or may not be felt while driving.
This bulletin applies to 2018 GMC Yukon and Yukon XL vehicles equipped with a 5.3L or 6.2L engine. A vehicle may have a concern of a misfire P0300 on Bank 1 that may or may not be felt while driving.
The timing may retard up to -16 degrees while the concern is duplicated. There may be a noticeable tapping noise from the engine at idle that could be heard while standing next to the vehicle.
This concern may be picked up as a knock activity on the affected cylinder(s) which is causing the ECM to retard timing on those cylinders. This can cause weak firing pulses on Bank 1 cylinders which contributes to counting misfires.
If this condition is found, inspect the HPFP lifter roller bearing for failure (making noises and/or looseness).
Information for Technical Service Bulletins comes from ProDemand, Mitchell 1's auto repair information software for domestic and import vehicles. Headquartered in San Diego, Mitchell 1 has provided quality repair information solutions to the automotive industry since 1918.
Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety ofspecialties, from engine building to wheel alignment, and has authored more than a dozen books that crisscross the automotive spectrum. Mike operates Birchwood Automotive, an Ohio shop that builds custom engines and performs vintage vehicle restorations. The shop also features a professional photo studio to document projects and to create images for articles and books.
