Chevrolet Says Suburban May Have Oil Pressure Problem
This bulletin applies to 2019 Chevy Suburban vehicles equipped with a 6.0L L96 engine. The engine may have a concern of no oil pressure and/or DTC P0521 set. This may be due to the relief valve in the oil pump sticking or there is damage to the number 1 main bearing.
Check the engine oil dipstick to confirm that the crankcase is not under or over filled. Confirm oil pressure at the main gallery with a manual gauge. If pressure is lower than specification, replace the oil filter.
If no improvement is found, remove the oil pan and inspect for number 1 main bearing damage. If the bearings are OK, change the oil pump. According to GM, engineering is currently working on a root cause.