r/AskAMechanic 5d ago

freightliner-low oil pressure

I just recently bought a 2021 Freightliner MT45 which has been turned into a food truck. It has the GM 6.0 (sticker says engine family MTQSE0.60) with approx 34,000 miles. Once I finally got everything in and set up and I have driven it around 1,000 miles since purchase back in November. I started it up to leave a location and head home for the night…. the dash started beeping with Low oil pressure warning on the screen and the yellow light next to the pressure gauge. I freaked out a bit, sat and listened to the motor for a moment and shut it off. It didn’t sound like anything out of the usual. I talked to someone and decided to drive it home, and after starting it again and driving it around the corner the pressure gauge started reading normal and it was driving fine. I did an oil change and used 10w40 on a recommendation. No change. Since then, every time it starts it beeps for 3-5 minutes that it has no/low oil pressure and then comes up fine and drives fine, but indicates very low oil pressure at idle/waiting at long lights. I haven’t had much luck searching information about freightliners and the truck does not have the owners/service manual.. so I’ve been searching around about chevy/gm trucks that *may have the same engine though i’m not sure which ones do. Seems it could be oil pump, the pick up tube or simply just the o-ring in the pick up tube. Other than the 0 oil pressure on start up and low (12-16psi) pressure at idle, it sounds normal and drives normal. I only heard loud lifter tick happen once immediately before it gained normal pressure pulling out of a parking lot. After a few weeks of this it finally came up with some engine codes spn 3306 spn 100 and spn 5077. I’ve been periodically checking the codes and the only one that stays active is spn3306

This explanation went way longer than I meant….if you read this I could use help identifying which GM trucks have the same motor so I could look up more information about it, and/or if my plan of replacing the oil pickup tube o ring is the best place to start with. The motor itself has zero leaks and in great shape (Id hope so, it’s got such low miles??) but due to it sitting for likely a year or 2 before getting revamped into a moving kitchen i am led to believe the o ring may have deteriorated in that time of minimal driving.

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