Service Repair

GMC Yukons May Misfire and Have Tapping Noise

Nov. 2, 2020

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.

Information courtesy of Mitchell 1

Mike Mavrigian

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).

About the Author

Information courtesy of Mitchell 1

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.

About the Author

Mike Mavrigian | Motor Age Editor

Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety of specialties, 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.