Mechanic messed with DOD system and can’t verify what they did
I have a 2014 Yukon Denali that is supposed to have the displacement on demand system. One of the lifters had failed on either cylinder 6 or 8. We took it to a mechanic and he supposedly decided to delete the dod system but won’t say exactly how he did it, even after taking him to court. We have a strong feeling he took used parts from another ls motor to do the repair as well. Long story short the car now runs terribly, will not idle, smokes, and exhaust gases are getting into the coolant system. I tried using my friends Marco scan tool to see if the system is still enabled but was not able to verify. The valley pan underneath the intake is smooth, but has a hose coming out that is blocked off with a bolt. I’m not able to drive the car to see if it still switches to v4 because the car will not run long enough to. I’m asking for advice as what to do next. Should I rebuild the motor and try to fully delete the dod system or should I try and restore everything back to how it was? Also how can I verify if the system is enabled or not through the computer? Thanks for any help in advance!