2020 Cascadia DD15 mil light leads one cylinder fails compression test

Measures voltage when cranking, a weak starter or batteries can also cause the reading to be off. Usually for a failed liner you will see like 5%, 79% would lead me to want to verify with a manual compression check and a cylinder leak down test.

 

Have the mechanic adjust the valves then re-proform the compression test. You're looking for a significant increase in compression in the two lowest cylinders. Traditionally, a valve adjustment is the first step in diagnosing a failing engine. If this does not solve the problem, you will know within the first 1,000 miles. I wouldn't call this truck a lemon. Just realize, every engine will not give you 1million miles no matter how well it is taken care of. Get what you can out of it then move on.

 

I have a 2018 frightliner cascadia. While driving on the high way my truck would switch to neutral and pause when it goes from 9th to 10th gear and 11th to 12th gear. It's ap problem getting up hill when this happens. I switched out the shifting control arm and it's still doing it. Anyone knows what might me going on? HELP ME.

 

I know GM has been doing this for years with the Duramax. They show the fuel balance rates off of baseline for each cylinder to maintain consistent idle speeds. If thay rate is out of sorts with other cylinders that data can be
Used to give a diagnostic starting point. But could be injector issue, mechanical concern etc.
One I diagnosed this winter had the balance rate for cyl 8 out of spec. Piston was cracked straight across over the wrist pin. No noise.

 

Unfortunately, manufacturers have made it almost impossible to diagnose these trucks correctly without being a rocket scientist. The best thing I can tell you is to keep taking it to the same dealership for repairs. Once your bill gets to $10k and the truck is stii not fixed, get a lawyer.