Inspect Chevy HPFP to Fix Misfire

This bulletin applies to 2018 Chevy Silverado, Suburban and Tahoe vehicles equipped with 4.3L, LV3, 5.3L L83 and 6.2L L86 engines. A concern of a misfire P0300 on bank one may occur that may or may not be felt while driving. The cause may be the HPFP lifter (high-pressure fuel pump lifter). Misfire counts may occur on all or multiple bank one cylinders. 

The timing may retard up to -16 degrees while the concern is duplicated. There may be a tapping noise 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 cylinders which is causing the ECM to retard timing on those cylinders. This can cause weak firing pulses on bank one cylinders, which contributes to counting misfires. If this condition is found, inspect the HPFP roller bearing for failures and repair as needed.